The Department of Foreign Affairs has confirmed that three Irish citizens were on board an Air France flight that has disappeared over the Atlantic Ocean.
It is believed the three are all women and are from Dublin, Belfast and Tipperary.
The Air France plane with 228 people on board disappeared on its way from Brazil to Paris after hitting strong turbulence.
French officials say they fear the worst.
Officials from the Department of Foreign Affairs have contacted the families of the Irish passengers and are offering full consular assistance.
The Irish embassies in both France and Brazil remain in close contact with the authorities investigating the disappearance of the flight.
Meanwhile, the Brazilian air force said the Airbus jet was well advanced over the sea when it went missing and military planes took off from both South America and Africa to hunt for the plane.
Air France said the airliner sent an automatic message reporting an electrical fault at 3.14am Irish time, roughly 15 minutes after the plane flew through a stormy area with strong turbulence.
Flight AF447 left Rio de Janeiro last night at 11pm Irish time and had been expected to land at Paris Charles de Gaulle airport this morning at 10.15am Irish time.
The carrier said 216 passengers were on board, including seven children and one baby, and 12 crew members. Air France said the pilots were highly experienced.
Senior French government minister Jean-Louis Borloo ruled out the possibility of a hijacking.
The jet's last known location was unclear and Brazil's Air Force said it lost contact with the plane at 3.14am.
The plane was an Airbus 330-200 powered with General Electric engines.
French president Nicolas Sarkozy has asked for assistance from US spy satellites in a bid to locate wreckage and try to discover how such a modern aircraft with state of the art communications and safety equipment could simply vanish.
Air France has set-up a special toll-free number for the attention of relatives and friends of passengers who may have been on board.
They can use this number to obtain information on whether or not a member of their family or friend was on board.
Phone number reserved for relatives and friends 0800 800 812 in France, 0800 881 20 20 in Brazil, and +33 1 57 02 10 55 for calls from all other countries.