If you're just joining our coverage of the incident in Jersey, this is what we know so far.
One person has been killed after an explosion at a block of flats just before 04:00 GMT, in St Helier, Jersey
Twelve people are missing, police say
Two people, described as "walking wounded", were taken to hospital
The three-storey building was completely destroyed in the blast, police say
Emergency services say a fire caused by the explosion has been extinguished.
Searches currently taking place at the scene are expected to take "a number of days", the island's Chief of Police Robin Smith says
The fire service attended the area last night because people had smelled gas, police say
Stay with us as we bring you more details.
People missing affects everyone in small community
Ammar Ebrahim
Reporting from Jersey
This explosion has sent shockwaves through the Jersey community.
Islanders were woken by the sound at 04:00, and smoke is still emerging from the building.
The search-and-rescue mission will continue for days, and the island will require the assistance of the UK.
In a small community like Jersey, an event like this is very distressing and with dozens still missing, there is significant concern among locals for those who are unaccounted for.
The health department urged people to avoid attending A&E unless they really needed to go as they were working to treat a large number of patients.
WATCH: Fire at the scene
Footage taken in the early hours of this morning shows the scene in St Helier following the blast that has killed one person and left 12 missing.
Police road closures were put in place after the explosion at Haut du Mont flats on Pier Road.
'Traumatising' experience of man rescued from flat
Luis was rescued from his flat by fire crews, along with his nephew, and evacuated to the St Helier town hall.
He told BBC Radio Jersey he felt “pretty shaken up but
OK, it’s traumatising that is”.
He and his nephew said they'd heard the other building had collapsed and that they "just hope their families are OK”.
WATCH: Considerable destruction at scene - police
Jersey's Chief of Police Robin Smith spoke to reporters about the extent of the damage to the property in St Helier that has left at least one person dead.
He said the three-storey building "completely collapsed" leaving a "pretty devastating scene".
Video content
Video caption: Jersey's Chief of Police Robin Smith describes the scene of the explosion in St HelierJersey's Chief of Police Robin Smith describes the scene of the explosion in St Helier
Blast felt like an earthquake - resident
One resident described being woken up by what she thought was an earthquake at about 03:50.
"The bed started to shake and there was this massive bang," she said.
"I checked online for news about an earthquake or lightning, I had no idea what it was."
In pictures: Blast hits St Helier
BBCCopyright: BBC
A large red fire could be seen coming out of a building in St HelierImage caption: A large red fire could be seen coming out of a building in St Helier
BBCCopyright: BBC
The blast happened in the early hours of SaturdayImage caption: The blast happened in the early hours of Saturday
BBCCopyright: BBC
Thick smoke could still be seen at the site of the explosion on Saturday morningImage caption: Thick smoke could still be seen at the site of the explosion on Saturday morning
Firefighters attended building last night
Firefighters were called to the building last night, the chief of police Robin Smith confirmed to reporters. He said he would not speculate as to why they were called, but said it would be addressed as a part of an ongoing investigation.
“As part of an investigation we
will look into that… and whether or not there was a safety issue.”He also warned there would likely be more fatalities from the explosion."There has to be a recognition that we could have more fatalities of course," he said.
Building collapse like 'a pancake just dropped'
The collapse of the building has been described as being like "a pancake that has just dropped almost sort of straight down" by the Jersey chief of police.
He told reporters the three-storey building "completely collapsed" and a nearby building was damaged as well.
The building is owned by Andium Homes, who say they are working with emergency services at the scene.
Incident will go on for number of days - police
A few minutes ago, Jersey's chief of police Robin Smith described the scene as "devastating and dangerous", adding that search and rescue efforts might take days.
“As I’m sure you will understand, the scene is a very
dangerous one for all of our staff as well.
“We’re using specialist resources to start to see if we can
see anybody trapped in the rubble.
“Thus far we have deployed around 21 police officers, nine paramedics attended that scene, nineteen firefighters - so a significant proportion of
our emergency services have deployed to that scene.
“This incident is going to go on for a number of days as we
continue a search and rescue operation.”
One killed in explosion in St Helier
This is what we currently know following the blast at a block of flats in the centre of St Helier.
Local police say one person has been killed and about 12 people are missing following the explosion just before 04:00 GMT.
Two people are being treated in hospital after the incident.
Searches at the scene are under way and Chief of Police Robin Smith said he expected it to take "a number of days".
A fire caused by the explosion has been extinguished and emergency services said about 20 to 30 people were being cared for at St Helier Town Hall.
Live Reporting
Edited by Jeremy Gahagan and Alexandra Fouché
All times stated are UK
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What's the latest?
If you're just joining our coverage of the incident in Jersey, this is what we know so far.
Stay with us as we bring you more details.
People missing affects everyone in small community
Ammar Ebrahim
Reporting from Jersey
This explosion has sent shockwaves through the Jersey community.
Islanders were woken by the sound at 04:00, and smoke is still emerging from the building.
The search-and-rescue mission will continue for days, and the island will require the assistance of the UK.
In a small community like Jersey, an event like this is very distressing and with dozens still missing, there is significant concern among locals for those who are unaccounted for.
The health department urged people to avoid attending A&E unless they really needed to go as they were working to treat a large number of patients.
WATCH: Fire at the scene
Footage taken in the early hours of this morning shows the scene in St Helier following the blast that has killed one person and left 12 missing.
Police road closures were put in place after the explosion at Haut du Mont flats on Pier Road.
'Traumatising' experience of man rescued from flat
Luis was rescued from his flat by fire crews, along with his nephew, and evacuated to the St Helier town hall.
He told BBC Radio Jersey he felt “pretty shaken up but OK, it’s traumatising that is”.
He and his nephew said they'd heard the other building had collapsed and that they "just hope their families are OK”.
WATCH: Considerable destruction at scene - police
Jersey's Chief of Police Robin Smith spoke to reporters about the extent of the damage to the property in St Helier that has left at least one person dead.
He said the three-storey building "completely collapsed" leaving a "pretty devastating scene".
Video content
Blast felt like an earthquake - resident
One resident described being woken up by what she thought was an earthquake at about 03:50.
"The bed started to shake and there was this massive bang," she said.
"I checked online for news about an earthquake or lightning, I had no idea what it was."
In pictures: Blast hits St Helier
Firefighters attended building last night
Firefighters were called to the building last night, the chief of police Robin Smith confirmed to reporters. He said he would not speculate as to why they were called, but said it would be addressed as a part of an ongoing investigation.
“As part of an investigation we will look into that… and whether or not there was a safety issue.”He also warned there would likely be more fatalities from the explosion."There has to be a recognition that we could have more fatalities of course," he said.
Building collapse like 'a pancake just dropped'
The collapse of the building has been described as being like "a pancake that has just dropped almost sort of straight down" by the Jersey chief of police.
He told reporters the three-storey building "completely collapsed" and a nearby building was damaged as well.
The building is owned by Andium Homes, who say they are working with emergency services at the scene.
Incident will go on for number of days - police
A few minutes ago, Jersey's chief of police Robin Smith described the scene as "devastating and dangerous", adding that search and rescue efforts might take days.
“As I’m sure you will understand, the scene is a very dangerous one for all of our staff as well.
“We’re using specialist resources to start to see if we can see anybody trapped in the rubble.
“Thus far we have deployed around 21 police officers, nine paramedics attended that scene, nineteen firefighters - so a significant proportion of our emergency services have deployed to that scene.
“This incident is going to go on for a number of days as we continue a search and rescue operation.”
One killed in explosion in St Helier
This is what we currently know following the blast at a block of flats in the centre of St Helier.
Local police say one person has been killed and about 12 people are missing following the explosion just before 04:00 GMT.
Two people are being treated in hospital after the incident.
Searches at the scene are under way and Chief of Police Robin Smith said he expected it to take "a number of days".
A fire caused by the explosion has been extinguished and emergency services said about 20 to 30 people were being cared for at St Helier Town Hall.
Read more here.
Welcome to our live coverage
One person has died after an explosion in a block of flats at Haut du Mont, Pier Road, in St Helier, Jersey.
About 12 people are missing and two "walking wounded" are being treated in hospital.
Stay with us as more news emerges.