Mexico prepared to turn the bodies of five Canadian tourists over to their relatives Monday as six people recovered from wounds suffered in a mysterious blast at a Caribbean coast hotel, where inspectors from the army, navy and civil defense agencies combed through the rubble looking for clues in the accident that also killed two Mexican hotel employees.

Experts and officials differed over whether the sprawling luxury hotel complex was in fact a palm-fringed Caribbean coastal time bomb, accumulating swamp gas since it was built four years ago over a mangrove thicket.

Quintana Roo state attorney general Francisco Alor said Monday investigators believe the explosion at the 676-room Grand Riviera Princess resort in Playa del Carmen, south of Cancun, was produced by gases from rotting vegetable matter or waste trapped beneath the ground floor of the building where the blast occurred.

The oxygen-deprived muck underlying mangrove swamps is known to produce methane gas, said Roberto Iglesias, a biologist with the Ocean Sciences Institute of Mexico's National Autonomous University who works on coral reefs and coastal environments in Puerto Morelos, not far from the resort of Playa del Carmen.

"We used to take students around outside ... and all you had to do was move the sediment a little, bubbles would come up and you could start flames when you lit them with a lighter," Iglesias said, adding that builders frequently cover swampy areas with a layer of crushed rock and concrete, which acts as a stopper that accumulates gas.

"I hope authorities that authorities pay more attention to this, because there are buildings constructed on top of mangroves all over," he said.

But some environmental officials consulted by The Associated Press, like Gabriela Lima, the head of the Environment Department for Quintana Roo state, where the resort is located, said the swamp-gas theory "sounds a bit strange."

"If that were the case, we'd have to see explosions throughout the Yucatan Peninsula every now and then, and we never have. This is something unique," Lima told the AP. Lima said construction permits for the hotel, built four years ago, were in order, though Mexican law no longer permits removing mangrove.

Playa del Carmen Civil Defense director Jesus Puc said the Grand Riviera Princess was built in a particularly swampy area. Puc's office is taking the gas theory seriously enough to request new equipment capable of detecting methane, and is planning to check other hotels in the area.

Puc said no gas was detected in an inspection of the Grand Riviera Princess four or five months ago, but the inspectors' equipment was designed to detect butane used in cooking, not the methane gas emitted by swamps.

Asked how many resorts could be at risk, Puc demurred, saying there are "many, many hotels in the area," though "not all of them have such swampy areas."

Ecologist and environmental activist Robert Cudney called the explosion a predictable consequence of constructing resorts in the mangrove swamps that line the coast of the posh Riviera Maya.

"It makes complete sense," said Cudney, who works with the environmental group Mexico Silvestre, based on the island of Cozumel just offshore from Playa de Carmen. "When you build over the mangrove ... it doesn't take away the whole ecological process that's going on there. You still have water filtration, you still have a lot of organic material. It's just one of those things that weren't taken into account and now (Mexican authorities) are going, 'Oops,'" Cudney said.

Adriana Rivera of the Office of the Attorney General for Environmental Protection said that in the agency's 18 years of existence, there was no record of a similar incident in a hotel, adding that such blasts are typically seen in factories or places where caustic or flammable materials are stored.

Sunday's blast blew out windows in a lounge area, littering the lawn with shards of glass and metal debris, and left behind a crater 3 feet (1 meter) deep.

Guests said it was so powerful it sucked the air out of the thatched-roofed buildings.

"The velocity of the air coming back was incredible, so people were thrown around all over the place in the rooms and hallways," said Carson Arthur, a 39-year-old from Toronto who was vacationing with six friends.

"There were several people in the debris. There was a lot of people wounded from flying glass," he said.

Among the dead was Malcolm Johnson, a real estate agent from British Columbia, who traveled to Mexico last week to get married, his friend David Komo said in an interview.

Johnson's new bride and 1-year-old daughter were with him in Mexico, Komo said.

Also killed were 41-year-old oil industry worker Chris Charmont and his 9-year-old son, John, from Alberta.

Family friend Tammi Garbutt said the two went down for something to drink right before the blast. Charmont's wife, Terra, and their 10-year-old daughter, Megan, stayed up in the room.

In addition to the dead, three Canadians and three Mexican employees remained hospitalized with injuries suffered in the blast. They were all in stable condition and were expected to recover, said Francisco Alor, attorney general of Quintana Roo.

Most guests were Canadians in town for a convention or sunny winter getaways.

After repeated calls, public relations representative for the Grand Riviera Princess hotel said she was not authorized to provide any additional details about the accident over the phone.

Tourism to Mexico, the nation's No. 3 source of foreign revenue, has only recently begun recovering from a downturn caused by soaring drug violence, last year's swine flu epidemic and the world economic crisis.

Canada's foreign affairs minister stopped short of discouraging travel to Mexico.

"It's an unfortunate accident. There's been loss of life. And it is a tragedy," Lawrence Cannon said in a news conference Monday in Montreal. "But I am sure that within the next few weeks and months, the government of Mexico will be able to shed all of the light on this incident."

[Linked Image]

In this photo released by 570 News via The Canadian Press, debris is seen scattered on the lawn of a resort hotel in Playa del Carmen, Mexico, Sunday Nov. 14, 2010. According to the Attorney General of the state of Quintana Roo, Francisco Alor, a blast at the hotel on Mexico's Caribbean coast, apparently caused by an accumulation of gas, has killed six people and left 15 wounded.