Armed forces chief Hadi Tjahjanto said a possible seabed location of the jet had been found during the search and rescue operation.
He told TV One: “We strongly believe that we have found a part of the fuselage of JT610.”
Mr Tjahjanto said search teams have location coordinates for what they believe is the crash site, but still need to confirm it is the fuselage.
He explained: “Yesterday afternoon the team heard a ‘ping’ sound in a location at 35 metres depth.
“This morning at 5am the team has gone back to dive at the location.”
Indonesian authorities had been using so-called “pinger locators” in an attempt to find the aircraft’s blackboxes, an informal term for its cockpit voice and flight data recorders.
The recorders send out “pings” designed to help investigators find the aircraft should it crash.
Previously some human remains had been discovered, but not the main fuselage of the black boxes.
The two-month-old aircraft crashed into the sea just 13 minutes after taking off.
It had 181 passengers and eight crew onboard.
Relatives of those affected have been providing DNA samples to help identify the bodies.
More to follow…