JAKARTA (AFP) - Weather was the "triggering factor" in the crash of AirAsia flight 8501 into the Java Sea a week ago with 162 people on board, according to Indonesia's meteorological agency.

The Airbus A320-200 crashed during a storm en route from Indonesia's second city Surabaya to Singapore, and relief workers are hunting for flight data recorders to determine the cause of the crash.

But an initial report on the website of BMKG, Indonesia's meteorological agency, suggests the weather at the time the plane went down sparked the disaster after it appeared to fly into storm clouds.

"Based on the available data received on the location of the aircraft's last contact, the weather was the triggering factor behind the accident," said a report on the agency's website.

"The most probable weather phenomenon was icing which can cause engine damage due to a cooling process. This is just one of the possibilities that occurred based on the analysis of existing meteorological data," it said.

"The waves are calmer, only one to two metres (three to seven feet) high," search and rescue official S.B Supriyadi told AFP, adding that 95 divers were on standby on various ships.

"We'll be concentrating on the underwater search, hopefully we'll be able to evacuate more bodies. We want to speed up the evacuation of bodies which might be stuck inside the plane's body," he said.

He said they would be using sonar equipment in their underwater searches, while aircraft would continue to scour the sea and coastline.

A presentation shown to reporters on Saturday described one of the debris pieces as the "suspected tail" of the plane, but strong currents had made it difficult to operate a remotely-operated underwater vehicle to get a picture of the objects, which are 30m underwater.

Before take-off, the pilot of Flight 8501 had asked for permission to fly at a higher altitude to avoid the storm, but the request was not approved due to other planes above him on the popular route, according to AirNav, Indonesia's air traffic control.

In his last communication, Captain Iriyanto, an experienced former air force pilot, said he wanted to change course to avoid the menacing storm system. Then all contact was lost, about 40 minutes after the plane had taken off.

Of the 162 passengers and crew on board, 155 were Indonesian, with three South Koreans, one Singaporean, one Malaysian, one Briton and a Frenchman - co-pilot Remi Plesel.

The families of victims have been preparing funerals as the bodies recovered are identified in Surabaya, where a crisis centre has been set up at a police hospital with facilities to store 150 bodies.

About 100 grieving Catholic relatives and well-wishers, some of them in tears, crowded into a small church in the police headquarters for a memorial mass Saturday afternoon, singing hymns and praying for the victims to be found quickly.

"We are trying to cope as hard as we can but it is still a very difficult time for our family as we are still waiting for news," said 25-year-old Mr Sebastian Joseph Widodo, whose sister Florentina was on the plane.

"My faith is very central, especially at this time where there's nothing much we can do," he added.

Major parts of the Airbus A320-200 were found in the sea off the island of Borneo late on Friday and Saturday, raising hopes that the remaining bodies and the crucial black box recorders would soon be located.

High seas throughout the week have hampered the relief process, a huge operation assisted by several countries including the United States and Russia, but divers were preparing to go down to the wreckage Sunday as the weather cleared.

"The waves are calmer, only 1m to 2m high," search and rescue official S.B Supriyadi told AFP, adding that 95 divers were on standby on various ships.

"We'll be concentrating on the underwater search, hopefully we'll be able to evacuate more bodies. We want to speed up the evacuation of bodies which might be stuck inside the plane's body," he said.

He said they would be using sonar equipment in their underwater searches, while aircraft would continue to scour the sea and coastline.

Indonesia has pledged to investigate flight violations by AirAsia, saying the ill-fated aircraft had been flying on an unauthorised schedule when it crashed. The airline has now been suspended from flying the Surabaya-Singapore route.