Sharm el-Sheik, Egypt ? A charter jet full of French tourists returning home from Egyptian vacations crashed early Saturday into the shark-infested Red Sea, killing all 148 people aboard. Officials blamed mechanical failure.

Egyptian Foreign Minister Ahmed Maher said the crash, which came as nations heightened security at airports and canceled flights because of terror threats, was “not related to any terrorist act.”

The Civil Aviation Ministry said the crash was an accident apparently caused by a mechanical problem.

French officials also said the crash appeared accidental. Deputy Transportation Minister Dominique Bussereau told reporters at Charles de Gaulle airport outside Paris that the pilot detected problems on takeoff and tried vainly to turn back.

Flash Airlines Flight FSH604 took off from the popular tourist resort of Sharm el-Sheik bound for Paris after a stopover in Cairo. The weather was clear at the time.

A French Foreign Ministry spokesman said there were 133 French tourists on the flight. One Japanese, one Moroccan and 13 Egyptian crew members also were on the flight, Egypt’s Civil Aviation Minister Ahmed Shafeeq said.

Distraught relatives of those aboard Flight FSH604 gathered at airports and travel offices in France and Egypt, desperate for news of their loved ones.

French Prime Minister Jean-Pierre Raffarin declared the nation in mourning and said investigators would go to Egypt to “shed light as quickly as possible on this catastrophe.”

Engineers from the national carrier EgyptAir rushed in to help with the investigation, and the United States also was sending an accident investigator, said Keith Holloway, a National Transportation Safety Board spokesman in Washington. He said Egypt requested the help.

A relative of a passenger on a plane that crashed in Egypt leaves the crisis center in a hotel near Roissy Charles de Gaulle airport, north of Paris. A charter airliner carrying 148 people -- mostly French tourists -- crashed into the Red Sea shortly after takeoff Saturday from the resort of Sharm el-Sheik. There were no reports of survivors.

Family members hoping to pick up passengers early Saturday at the French airport were discreetly pulled aside by authorities and taken by shuttle bus to a nearby hotel.

Looking pale and shaken, a couple in their 50s arrived at the terminal, where the man asked an airport official: “My children are at Sharm. How do I find out if they were on the plane?”

Most of the passengers were on a tour organized by FRAM, one of France’s largest travel operators. FRAM said it had 125 people — mostly families or groups of friends — on the flight.

According to the radar images, the plane turned left as normal after takeoff, then suddenly straightened out and turned right before plunging into the sea, one minute after its left turn, Shafeeq said.

Earlier, he told state-run television: “There was a malfunction that made it difficult for the crew to … save the plane.”

Shafeeq said the depth of the water — at least 1,000 feet — complicated retrieval efforts but some bodies, as well as airplane wreckage, were found. A marine official in a nearby port said at least 50 body parts were found.

Tourists in swimsuits watched from the beach as rescuers circled the waters in small boats looking for survivors. They found only bodies, body parts and debris, including suitcases, shoes, life preservers and small bits of plane wreckage.

Egypt’s Middle East News Agency reported that blood was seen in the water because sharks ate some victims.

Flash Airlines said in a statement that the wreckage was found about nine miles from the airport, according to the Egyptian news agency MEAN.