A passenger jet full of French tourists plunged into the Red Sea Saturday because of an unspecified mechanical problem, officials said. All 148 people on board were killed.

Egyptian and French authorities quickly ruled out a terrorist attack, although the exact cause of the crash was not released.

"There was a malfunction that made it difficult for the crew to ... save the plane," Egypt's Civil Aviation Minister Ahmed Shafeeq told state-run television.

A relative leaves the Hotel Ibis crisis centre in Paris (AP photo)

The Boeing 737, belonging to Egyptian charter company Flash Airlines, disappeared from radar screens minutes after taking off from the resort of Sharm el-Sheik. The plane was headed to Paris with a scheduled stop in Cairo.

"The incident is absolutely not the result of a terrorist act, but is linked to a technical failure of the plane," said Egyptian Foreign Minister Ahmed Maher.

The French foreign ministry said 133 of the people aboard were from France. Many families with children were among those killed. They had been returning from vacations in Egypt.

Jean-Pierre Raffarin

In Paris, French Transport Minister Gilles de Robien said there was nothing to indicate that the cause of the crash was anything but an accident. French President Jacques Chirac called his Egyptian counterpart Hosni Mubarak shortly after the crash to get information.

The aircraft had problems taking off and crashed while trying to return to the airport, Deputy Transport Minister Dominique Bussereau told reporters in Paris.

Authorities at Charles de Gaulle airport took relatives of the victims to a nearby hotel for counselling and medical treatment for shock. Most had already heard about the crash on the news early Saturday. But a handful turned up, still expecting to greet family members returning from their holiday.

For some relatives, however, there were scenes of happiness and relief when they were reunited with passengers who had been bumped from the flight. They arrived home on a second charter.

French Prime Minister Jean-Pierre Raffarin and Transport Minister Gilles de Robien went to the airport to offer condolence.

"I am personally overwhelmed by this tragedy," the prime minister said, and he declared his country in a state of mourning.

France sent a team of experts to Egypt to help with the investigation and to retrieve the aircraft's black box, now a kilometre under water.