An investigator with Indonesia's National Transportation Safety Committee (KNKT) said the Sriwijaya Air jet that crashed into the Java Sea with 62 people on board over the weekend possibly broke apart when it hit waters based on debris found so far.
"We don't know for sure, but if we look at the debris, they're scattered in an area that is not too wide," Nurcahyo Utomo told Reuters on Monday.
"It possibly ruptured when it hit waters because if it had exploded mid-air, the debris would be distributed more widely," he added.
The Boeing 737-500 was headed on a domestic flight to Pontianak in West Kalimantan on Saturday before it disappeared from radar screens four minutes after take-off. There are no clues yet as to what caused the crash.
KNKT chief Soerjanto Tjahjono on Sunday said the locations of Flight SJ182's two black boxes had been identified.
"Hopefully, we can retrieve them soon," said military chief Hadi Tjahjanto, without giving an estimated timeframe.
Pieces of wreckage were brought to Jakarta port by rescuers, including the plane's altimeter radar, emergency chute and a piece that was suspected to have come off of the bottom part of the plane's tail, KNKT official Nurcahyo Utomo said.
One twisted piece of metal was painted in Sriwijaya Air's blue and red colours. Authorities said they came from a depth of 23m near a group of islands off the Jakarta coast.
Indonesian authorities said they had also retrieved body parts and clothing.
Police asked families to provide information such as dental records and DNA samples to help identify bodies.
The plane had 12 crew and 50 passengers on board, all Indonesians and including 10 children.
Tracking service Flightradar24 said the aircraft took off at 2.36 pm local time (3.36 pm Singapore time) and climbed to reach 10,900 feet within four minutes. It then began a steep descent and stopped transmitting data 21 seconds later.
There were no immediate clues on what caused the sudden descent. Most air accidents are caused by a cocktail of factors that can take months to establish, safety experts say.
A transport ministry spokeswoman said air traffic control had asked the pilot why the plane was heading northwest instead of on its expected flight path seconds before it disappeared.
The pilots had decades of experience between them with the flight captain reported being a former air force pilot and his co-pilot at Sriwijaya Air since 2013, according to his Linkedin profile.
The Sriwijaya Airplane was a nearly 27-year-old Boeing 737-500, much older than Boeing's problem-plagued 737 MAX model. Older 737 models are widely flown and do not have the stall-prevention system implicated in the MAX safety crisis.
"We are in contact with our airline customers and stand ready to support them during this difficult time," Boeing said in a statement. "Our thoughts are with the crew, passengers, and their families."
Founded in 2003, Jakarta-based Sriwijaya Air group flies largely within Indonesia's sprawling archipelago. The budget airline has had a solid safety record, with no onboard casualties in four incidents recorded on the Aviation Safety Network database.
In 2007, the European Union banned all Indonesian airlines following a series of crashes and reports of deteriorating oversight and maintenance since deregulation in the late 1990s. The restrictions were fully lifted in 2018.