Investigators say nothing has been ruled out as the cause of a plane crash in Venezuela which killed 160 people.
Relatives have been told it could take days to identify all the victims
Venezuelan officials are working with French and Colombian counterparts to study the jet's engines, both of which failed, and its flight data recorders.
More than 250 relatives from the French island of Martinique - home to most of the victims - attended a mass in their memory near the crash site on Sunday.
They have been told it could be days before all the bodies are identified.
The Colombian-owned West Caribbean Airways MD-82 crashed last Tuesday on a flight from Panama after the pilot reported problems in both engines.
Lt Col Lorllys Ramos, head of the Venezuelan aviation accident investigation unit, said officials would try to reconstruct the engines to discover what led both to fail at the same time.
She said it was too early to rule out any potential cause, including a lack of fuel.
"The investigation will cover everything - the material factors, the human factors, the weather conditions - we can't leave out any element," she told Reuters news agency.
A prayer service was held to remember the 160 people killed
Meanwhile, French daily Le Monde reported that France was unaware the Colombian airline had been fined for safety violations in January until after the crash.
Michel Wachenheim, general director of France's civil aviation authority, told the newspaper Colombia had not notified any other countries about the fines.
It is not a legal requirement to do so, he said, but added: "If we had known it might have provoked a question from us, like asking Colombian authorities for more information."
The remains of the eight crew members, all Colombian, were quickly identified and flown to Colombia on Saturday.
But officials have warned it could take up to three weeks to identify all 152 French passengers, using fingerprints and dental records, so their bodies can be returned home.
Hundreds of relatives and friends went to the morgue in the Venezuelan city of Maracaibo, nearest to the crash site, to lay red roses on Sunday. Some demanded answers about the cause of the crash.
A prayer service was held nearby and more flowers were laid at a monument to the dead put up in Maracaibo's La Chinita cemetery.
France's President Jacques Chirac will fly to Martinique on Wednesday to attend a day of mourning in memory of those killed.
West Caribbean Airways was set up in 2000 to provide low-cost flights within Colombia and to the Caribbean region, according to the company website.
This is the second incident this year involving the airline. In March, a flight taking off from the Colombian island of Providencia crashed, killing eight people.