Weather was the "triggering factor" in the crash of AirAsia Flight 8501 with icing likely causing engine damage, Indonesian officials said, as rough seas Sunday hampered the search for bodies and the sunken wreckage.
The Airbus A320-200 crashed into the Java Sea a week ago carrying 162 people from Indonesia's second city Surabaya to Singapore, and relief workers are hunting for the "black box" flight data recorders to determine the cause of the crash.
An initial report on the website of Indonesia's meteorological agency BMKG suggested 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 the report, which referred to infra-red satellite pictures showing peak cloud temperatures of minus 80 to minus 85 degrees celsius at the time.
"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," the report said.
It remained unclear why other planes on similar routes were unaffected by the weather, and other analysts said there was not yet enough information to explain the disaster.
"It's irrelevant to make an assumption on the cause of the crash as we haven't found the black boxes yet," former air force commander Chappy Hakim told AFP.
Five major parts of the Airbus A320-200 have now been found off the island of Borneo, but rough weather throughout the week has hampered the search, a huge operation assisted by several countries including the United States and Russia.
During a momentary respite from bad weather, a team of divers went down to the biggest part of the wreckage Sunday morning and recovered one body, while another three were found floating in the sea, bringing the total number of bodies recovered to 34.
The divers "managed to go down but the visibility at the sea bottom was zero, it was dark and the seabed was muddy, with currents of three to five knots," search and rescue agency chief Bambang Soelistyo told reporters, adding that heavy rain and big waves were continuing to impede the rescue effort.
"For that reason, the diving efforts must be temporarily stopped. We'll try to deploy an ROV (remotely-operated underwater vehicle)," he said.
He said the fifth major part of the plane, located early Sunday, was about 10 metres by one metre (33 by 3.3 feet).
The search, focused on a patch of sea southwest of Pangkalan Bun, a town on Borneo, has also been extended east because parts of the plane may have been swept by currents, Soelistyo said.
The relief operation has prioritised finding the bodies of those on board the ill-fated flight, of whom 155 were Indonesian, with three South Koreans, one Singaporean, one Malaysian, one Briton and a Frenchman -- co-pilot Remi Plesel.
Indonesian warship commander Yayan Sofyan told MetroTV Sunday that three of the bodies so far recovered had been found still strapped into their row of seats, detached from the main plane body.
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.
Hendra Gunawan Syawal, 23, had been on his way for a New Year's Eve break in Singapore with friends when the plane crashed. His relatives were readying for his last Buddhist rites.
"Even after days, we still kept thinking he's alive, but now that we have seen his body, we know he's gone for sure," said his sister Yunita.
"There is a void left in my heart, but I hope in time I will heal."
Indonesia has pledged to investigate flight violations by AirAsia, saying the aircraft had been flying on an unauthorised schedule when it crashed. The airline has now been suspended from flying the Surabaya-Singapore route.
But the Civil Aviation Authority of Singapore said it had granted permission for the airline's Sunday flight.
It was unclear how the airline, a unit of Malaysia-based AirAsia, had been able to fly without the necessary authorisation from its starting point.
The company has declined to comment until the probe is complete, but said it would "fully cooperate" with the government.
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.