While the KNKT confirmed that the locations of Flight SJ182's two black boxes had been pinpointed, the cause of the crash is yet to be identified.
Black box data - which record information about the speed, altitude and direction of the plane as well as flight crew conversations - helps explain almost 90 percent of all crashes, according to aviation experts.
He said the divers also found the underwater acoustic beacon, a device attached to aviation flight recorders, of the cockpit voice recorder, but the device itself has not been found.
It was unclear whether the device was the plane's flight data or cockpit voice recorder.
The Boeing 737-500 plane with 62 people on board plunged into the Java Sea on Saturday, four minutes after taking off from Jakarta's main airport.
"We strongly believe it'll be found soon", he said.
While the remote-controlled vehicles scoured the seabed, navy vessels with sonar searched from the surface.
National Police spokesman Rusdi Hartono said about 53 samples for DNA testing have been collected but more are still needed, especially from parents and children of victims.
"Our family is still hoping for a miracle that he is still alive".
The effort has so far retrieved multiple human body parts and one crash victim has been identified.
"Heaven is your place, dear ... be peaceful there".
The plane had been headed to Pontianak on Borneo island, about 740 km (460 miles) from Jakarta.
Search-and-rescue agency chief Soerjanto Tjahjono echoed that view earlier Tuesday, pointing to the relatively small area where debris was scattered in about 23 metres (75 feet) of water.
Members of the National Transportation Safety Committee carry a box containing the flight data recorder from the Sriwijaya Air flight SJ-182 retrieved from the Java Sea.
"The size is consistent with the assumption that the plane didn't explode before hitting the water", he added.
"The damage on the fan blade showed that the engine was still working on impact".
It was still functioning and intact before it crashed, preliminary results showed.
Sriwijaya Air has had only minor safety incidents in the past, though a farmer was killed in 2008 when a plane went off the runway while landing due to a hydraulic issue.
But it has not had a fatal crash since starting operations in 2003.
The disaster has reignited concerns about safety in the aviation industry, which grew quickly after the economy was opened following the fall of dictator Suharto in the late 1990s.
In October 2018, a B-737 MAX 8 operated by low-priced carrier Lion Air crashed off the northeast coast of Jakarta immediately after takeoff, killing all 189 passengers and crew.