EgyptAir has changed the picture on its Facebook page to plain blue, in what seems like a reference to the missing plane.

Image source, Facebook

Image source, AFP/Getty Images

France's Prime Minister Manuel Valls has been speaking to RTL radio in the past hour.

"We are in close contact with the Egyptian authorities, both civil and military," he said.

"The Egyptian authorities have already sent air reconnaissance teams to the site, and France is ready to help with the search if the Egyptian authorities ask, of course.

"At this stage, no theory can be ruled out regarding the causes of the disappearance."

The flight was travelling between Paris and Cairo, with 15 French passengers on board.

Reporters have started gathering at the EgyptAir counter at Charles de Gaulle airport in Paris.

Image source, Associated Press

Reuters are reporting comments from French President Francois Hollande's spokesman - he says Mr Hollande and his Egyptian counterpart Abdul Fattah al-Sisi have spoken, and will "co-operate closely" in the investigation.

There's been some more response in France too.

If you're just joining us, here is the latest news on flight MS804.

• The Airbus A320 was travelling from Paris to Cairo when it disappeared from radar at around 02:45 Cairo time (01:45 BST)

• It was some 16km inside Egyptian air space when it went missing, and was about half an hour from landing
• The last contact with the plane showed it was over the Mediterranean, to the south of the area between the islands of Crete and Cyprus
• EgyptAir says there were 56 passengers on board: they included 30 Egyptians, 15 French and 10 other nationalities, including one Briton
• There were also 10 crew members on board
• Anyone concerned can call 0800 7777 0000 from any landline in Egypt and +202 259 89320 from any mobile phone or from outside Egypt  

The Wall Street Journal's aerospace and Boeing reporter tweets:

Image source, AP

It's now five hours since contact was lost with flight MS804, and the families of those on board have started to arrive at Cairo's airport, where it had been due to land.

Prime Minister Sherif Ismail has also arrived there, Egyptian media report.

There were 30 Egyptian passengers on board, EgyptAir says.

EgyptAir has just posted a tweet confirming the nationalities of the passengers.

There are 15 French, 30 Egyptian, one Briton, one Belgian, two Iraqis, one Kuwaiti, one Saudi, one Sudanese, one Chadian, one Portuguese, one Algerian and one Canadian.

Egypt's state-run newspaper Ahram has quoted an airport official as saying the last contact with the plane was 10 minutes before it disappeared from radar.

Egypt's ON TV says ships belonging to the Egyptian Armed Forces are now being deployed to the Mediterranean, in co-operation with Greece.

Greece has joined the search and rescue operation for the EgyptAir flight, Associated Press reports.

Flight trackers show flight MS804 disappeared roughly to the south of the region between the islands of Crete and Cyprus.

Two aircraft, one C-130 and one early warning aircraft have been dispatched, officials at the Hellenic national defence general staff said.

They said one frigate was also heading to the area, and helicopters are on standby on the southern island of Karpathos for potential rescue or recovery operations.

Sally Nabil
BBC News, Cairo

The authorities haven't said exactly where the plane is believed to have disappeared, but it was shortly after entering Egyptian airspace.

They are usually very cautious when it comes to publishing information in relation to aviation accidents, because of fears it might inflict more damage on the tourism industry, which is a lifeline to the Egyptian economy.

EgyptAir has set up helpline numbers for passengers' relatives. Anyone concerned can call 0800 7777 0000 from any landline in Egypt and +202 259 89320 from any mobile phone or from outside Egypt.

Authorities at Charles de Gaulle airport in Paris have not yet commented.

Image source, Reuters