Investigators lifted scraps of metal and crouched among charred trees Wednesday, searching for victims' remains while trying to piece together what could have caused both engines to fail in Venezuela's deadliest air disaster.

Officials said it could take time to identify the scattered remains of the 160 victims, mostly vacationers headed home to the French Caribbean island of Martinique when the West Caribbean Airways (search) jet crashed.

The plane appeared to have "hit the ground in a nosedive at full force," French Foreign Minister Philippe Douste-Blazy (search) said in Paris.

Venezuelan investigators were focusing on the possibility of contaminated fuel, or some other fuel problem that led both engines to fail simultaneously, said Nelson Serrano, an emergency official in the western state of Zulia where the crash occurred.

Investigators took samples from what remained of the engines, but "the near-total destruction of the plane makes this investigation tough," police investigator Hernan Zurita said.

"The one thing that can cause an engine like that to have a problem is fuel contamination," said Paul Czysz (search), emeritus professor of aerospace engineering at St. Louis University in the United States. "It could be water. It could be any number of things."

Panamanian authorities, however, said they found no evidence of tainted fuel and that the plane had plenty of fuel for the three-hour trip.

The focus on the engines and the fuel stems from the pilot's radio call shortly before the crash. He said both engines had failed and requested permission for an emergency landing.

Venezuelan officials said they believed the McDonnell Douglas MD-82 (search) fell into a steep descent minutes later and slammed into the ground east of the Sierra de Perija mountains near Machiques, about 400 miles west of Caracas.

The jet was carrying 152 tourists from Martinique returning home after a week in Panama, officials said. All eight Colombian crew members were also killed.

The plane's tail jutted from the ground at the crash site, where more than 100 workers fanned out Wednesday, cutting through toppled trees with chain saws and collecting body parts strewn among the scraps of metal.

"There are still bodies out there and we'll be working until none are left," firefighter Romer Morales said.

French officials have said many of the victims may only be identified through DNA.

The crash was the deadliest in Venezuelan history, according to the Aviation Safety Network, a nonprofit group that keeps a database of air disasters. It said the death toll surpassed a 1969 crash in Venezuela that killed 155, including 71 victims on the ground.

Search teams recovered the jet's two black boxes, including the cockpit voice recorder, which was expected to provide important clues about the crash, said Col. Antonio Rivero, chief of Venezuela's emergency agency.

In Martinique, relatives and friends of the victims prayed at a memorial ceremony. French Minister of Overseas Departments Francois Baroin tried to comfort mourners, hugging a crying girl who had lost her parents. Several elderly people collapsed in grief.

"I urge a swift investigation to determine what happened," Baroin said. "And I hope it never happens again."

Some passengers were descendants of workers who helped build the Panama Canal a century ago, said Alina Guerrero, a spokeswoman for Panama's Foreign Ministry. She said the group chartered the flight for a program to visit descendants of the Caribbean immigrants who worked on the canal.

French specialists were sent to Venezuela to join the investigation and help identify victims' remains, officials said.

The U.S. government offered help in the investigation, as did Boeing Co., (search) which merged with McDonnell Douglas in 1997. Jim Proulx, a company spokesman, said the plane was built in 1986.

The Medellin, Colombia-based West Caribbean began service in 1998. Another of its planes crashed in March during takeoff from the Caribbean island of Old Providence, killing eight.

It also has a record of mechanical problems and financial troubles, but airline officials insist they did not cut corners on safety. Airline spokesman John Ospina said the aircraft passed all safety inspections Monday night in Colombia before heading to Panama for its flight.

The crash came two days after a Cypriot airliner crashed in Greece, killing all 121 people aboard. Both jets were flying for new, low-cost regional carriers that are springing up around the world as governments deregulate air travel.