Indonesia's military said Wednesday that search teams had detected an object thought to be the fuselage of a passenger jet that crashed into the Java Sea with 189 people on board. 

A naval ship's sonar sensor detected a 22-metre object at a depth of 32 metres on the seabed, senior naval officer Haris Djoko Nugroho told local news channel TVOne.  

Divers would be sent to inspect the object, he said. 

Air Chief Marshal Hadi Tjahjanto said earlier that he hoped the object was the aircraft's fuselage. 

The Boeing 737 MAX 8, operated by budget carrier Lion Air, crashed on Monday about 13 minutes after take-off from Jakarta's Soekarno-Hatta International Airport. 

All 181 passengers and eight crew members are presumed dead.

The captain of a tug boat told local television that he saw the ill-fated Lion Air plane as it crashed into the Java Sea and disintegrated on impact. 

"The aircraft crashed with a loud explosion," Rahmat Slamet told TVOne. "I didn't see the body of the plane on the water but saw the tail as it was sinking."

Rahmat said he was about one mile from the crash site and ordered his crew to wear their life vests to rescue crash victims. 

He also radioed authorities at Jakarta's Tanjung Priok port. 

"As we approached the location, debris such as seats, life vests, tubes and things belonging to passengers came to the surface," he said. 

Ten additional ships were deployed on Wednesday as the search for bodies and the aircraft's hull entered a third day, bringing the number of vessels involved to 44, the National Search and Rescue Agency said. 

The aircraft was bound for Pangkal Pinang in the province of Bangka-Belitung Islands when it crashed. 

The website aviation-safety.net said the aircraft logged "unreliable" readings of altitude and airspeed on its previous flight, the night before it crashed. 

A technical log for that flight, obtained by the website read: "Airspeed unreliable and alt disagree shown after take off," the report said.

Lion Air chief executive Edward Sirait confirmed to dpa Tuesday the plane had experienced the issues reported by the website on its previous flight, "but the problems were resolved overnight."