The fuselage, or main body, of the plane is believed to have been found by a ship scanning for wreckage northeast of where the tail section was previously discovered, said Supriyadi, an operations coordinator at Indonesia's national search and rescue agency who goes by only one name.
But he said he hasn't seen the full report on the reported discovery yet -- and it hasn't been confirmed so far by the head of the search and rescue agency.
The discovery of the fuselage would be a significant development as officials have suggested that many of the bodies of those on board the plane are likely to be found with it.
Forty-eight bodies have so far been recovered from the sea, some of them still strapped into seats. But more than 100 remain missing.
The overwhelming majority of the people on Flight QZ8501 were Indonesian. There were also citizens of Britain, France, Malaysia, Singapore and South Korea.
Black boxes contain the what and the why
On Tuesday, divers retrieved the cockpit voice recorder, which is designed to retain all sounds on a plane's flight deck.
The device is expected to help investigators understand what went wrong aboard Flight QZ8501, which went down in the Java Sea last month with 162 people aboard as it was headed toward Singapore from the Indonesian city of Surabaya.
On Monday, searchers recovered the plane's other key information source, the flight data recorder
, which stores a vast amount of information about the aircraft's performance, including air speed and cabin pressure.
The flight data recorder tells investigators what happened on a plane, but the cockpit voice recorder tells them why, said Mardjono Siswosuwarno, a senior official at Indonesia's National Transportation Safety Committee, which is leading the investigation into the disaster.
"The why is mostly in there," he said of the voice recorder, which captures conversations between pilots as well as other sounds in the cockpit.
Analysis of data to take months
The two flight recorders have been taken to a lab in Jakarta, the Indonesian capital, for analysis.
Investigators say they have successfully downloaded the contents of both devices. But Mardjono cautioned that interpreting the information requires much more time.
After the download, investigators should have "a pretty good idea within a couple of days" of what happened aboard the plane, Mary Schiavo, a former inspector general of the U.S. Department of Transportation, said this week.
The flight data recorder usually contains hundreds of parameters and thousands of data points, she said, that look a bit like an electrocardiogram when they're printed.
Mardjono said he expected a preliminary report to be released within a month of the crash, which happened December 28.
But it's unclear how much information the initial document will contain beyond what's already been made public. The final report containing investigators' full conclusions will take months, Mardjono said.
The agency's final report into Adam Air Flight 574 -- which crashed in Indonesian waters on New Year's Day 2007, killing all 102 people on board -- came out more than a year after that disaster.
Mardjono said the AirAsia plane's flight data recorder was in good condition after being pulled out of the water from under the debris of a wing Monday.
Did plane break apart on impact?
The recovery of the flight recorders took place after the plane's tail was lifted from the waves Saturday.
Observers have suggested that the locations of the different parts of debris indicate the plane broke apart when it hit the water, not when it was still at a high altitude.
Supriyadi, the Indonesian search official, said Monday that the debris patterns suggest the aircraft "exploded" on impact.
But the country's transportation investigators said it was premature to say what had happened, and one expert questioned the search official's choice of words.
"The word 'exploded' I think maybe loses a little bit in translation," said David Soucie, a former Federal Aviation Administration safety inspector. "I think really what he's meaning is a rupture from the impact itself.
"As with any hollow object hitting something very hard, the pressure differential between the outside and the inside is very significant, and it'll actually tear apart the aircraft on the top," Soucie said. "That may be what he's referring to."