Numerous fire engines at scenepublished at 15:13
Reports suggest up to 20 appliances were deployed to the Celsa site
Image source, Wales News ServiceSummary
Two people die in blast at Celsa Steel UK in Cardiff
Five people injured
Four of the casualties treated at University Hospital of Wales
Health and Safety Executive assisting police with investigation
Emergency services were called at 10:30 GMT on Wednesday
Numerous fire engines at scenepublished at 15:13
Image source, Wales News Service'Difficult time'published at 15:20
Carwyn Jones addresses assembly
Quote MessageI'm sure all members will join me in expressing our concern and of course to join with me in sharing our thoughts with the employees and their families at this very worrying and difficult time.
Carwyn Jones, First Minister
Explosion updatepublished at 15:08
South Wales Police is expected to make an updated statement on the Celsa explosion between 16:15 and 16:45.
Image source, Wales News ServicePolice vanspublished at 14:55
BBC Wales' Dave Dulin at the scene
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End of twitter post'We're lucky'published at 14:52
A worker at a nearby factory, who did not want to be named, said: "All we could hear was a big bang and the ground shook.
"It seemed like someone had driven into the side of the building.
"When we came outside you could see smoke coming from the top of the building.
"We have contractors going in and out of there every day so we were lucky."
'Awful news'published at 14:36
Labour MP for Pontypridd tweets
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End of twitter postExplosion felt half a mile awaypublished at 14:27
Charity boss heard bang
The explosion was felt at the office of first aid charity St John Cymru Wales, which is about half a mile away from the plant.
Chief executive Keith Dunn said: "I was interviewing some staff this morning and we heard a loud bang. The building and the windows shook."
The charity trains first-aiders at the Celsa plant.
Mr Dunn added: "Obviously our thoughts are with them and we will be making contact with the company to see if we can offer assistance."
Image source, Wales News ServiceLatest images from the scenepublished at 14:21
Emergency services remain at Celsa's Splott plant
Image source, Wales News Service
Image source, wales
Image source, Wales News Service'Major incident' stood downpublished at 14:17
Cardiff and Vale University Health Board has stood down major incidents protocols which were initiated in the aftermath of the explosion.
Chief operating officer Alice Casey said: "We have received four casualties from the incident and they are currently being assessed and treated by the trauma team at the emergency unit at University Hospital of Wales.
"We would like to thank our staff for their professional and efficient response to this incident and our partners and the public for their support."
'Explosion felt through floor'published at 14:12
BBC Wales' Natalie Crockett speaks to witnesses at scene
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End of twitter postA major employerpublished at 14:11
Background on what Celsa does and how many people it employs in Wales.
Image source, Wales News Service'Safe recovery' hopespublished at 14:08
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End of twitter post'No more casualties'published at 14:00
Dr Graham Shortland, medical director at University Hospital of Wales, said: "We were called just before 11:00 GMT by the police who announced a major incident.
"Since then, we've been receiving casualties into the A&E. We have received four casualties.
"At present I'm advised that we will not be receiving any more at this time."
'Hell of a bang'published at 13:57
Worker heard explosion
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End of twitter post'Cause of explosion'published at 13:55
Rob Edwards, of the union Community, said he believed an oil accumulator in the basement of the building had exploded.
Image source, Wales News Service'Thoughts with steel workers'published at 13:55
Plaid shadow economy minister tweets
Quote MessageMy thoughts with Celsa Steel workers in Cardiff & their families after this morning's explosion.
Rhun ap Iorwerth, Plaid Cymru AM
Concern over missing pairpublished at 13:46
Rob Edwards, from Communityunion, said news two people were missing at the site was "a concern".
Witness 'heard a rumble'published at 13:45
Peter Sestanovich, who was nearby when the explosion happened, said: "We heard a big bang and a rumble through the floor and we saw black smoke billowing over the top of buildings."
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End of twitter post'Worrying news'published at 13:42
South Wales East AM Mohammad Asghar
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End of twitter post'Quite a bang'published at 13:39
Julie Hughes, a director at Stratum, which is opposite Celsa, said: "It was quite a bang. It sounded like something landing on our roof.
"We saw the smoke. I was sat in reception seeing all the ambulances coming down the road. There are police lining up on East Moors Road."