Indonesian divers on Sunday recovered a large quantity of aircraft parts, debris and human remains from the area where a Sriwijaya Air Boeing 737 jet crashed into the sea off Jakarta with 62 people on board, including ten children.

The extensive search operation involving 2,500 rescuers and military personnel also led to the location of two black boxes from the plane, which contain key recordings to help investigators determine the causes of the crash which are still unknown.

“We have located the position of the black boxes,” said Soerjanto Tjahjanto, head of a committee in the Ministry of Transport. “Divers will start looking for them and I hope it won’t take long to recover them”.

Flight SJ182 lost contact with air traffic controllers on Saturday, minutes after taking off from Indonesia’s capital on a domestic flight.

Transportation Minister Budi Karya Sumadi said on Saturday that the flight was delayed for an hour before it took off at 2.36 pm local time (8.36 am CET).

The Boeing 737-500 disappeared from radar screens four minutes later after the pilot contacted air traffic control to ascend to an altitude of 8,839 meters, he said.

Flight tracker website FlightRadar24 showed SJ182 losing more than 10,000 feet of altitude in under a minute.

The plane was on a 90-minute flight from Jakarta to Pontianak, the capital of West Kalimantan province on Indonesia’s Borneo island, when it disappeared.

Hopes of finding survivors dashed

Indonesian President Joko Widodo expressed “his deep condolences” and called on his fellow citizens to “pray together for the victims to be found”.

Rescue workers said on Sunday evening that they recovered ten bags of human remains, as well as sixteen large pieces of fuselage and ten bags of debris.

Among the debris brought back to Jakarta’s main port were an aircraft tyre, pieces of fuselage in the company’s colours and a child’s pink clothing.

But the anguish of relatives was growing as hopes of finding survivors from the flight to Pontianak were dwindling.

Among the missing were a newly-married couple, Ihsan Adhlan Haki and his wife Putri.

“He called me to tell me that the flight was delayed due to bad weather,” said Arwin, the groom’s brother, from Pontianak where a ceremony was planned for the couple. “That was the last time I had contact with him”.

Among the passengers were also Beben Sofian, a 59-year-old Indonesian woman, and her husband Dan Razanah, 58.

“They made a selfie and sent it to their children before taking off,” their nephew Hendra told AFP.

Fifty passengers, including ten children, in addition to the twelve crew members, all Indonesians, were on board the plane.

Search and rescue operation launched

A dozen vessels, including four warships, were deployed in a search and rescue operation on Saturday centred between Lancang island and Laki island, part of the Thousand Islands chain just north of Jakarta, Sumadi said.

Bambang Suryo Aji, the National Search and Rescue Agency’s deputy head of operations and preparedness, said rescuers collected plane debris and clothes that were found by fishermen. These items were handed over to the National Transportation Safety Committee for further investigation to determine whether they were from the missing plane.

A commander of one of the search-and-rescue ships who goes by a single name, Eko, said that fishermen found cables and pieces of metal in the water.

‘Sound of thunder’

“The fishermen told us that they found them shortly after they heard an explosion like the sound of thunder,” Eko was quoted by TVOne as saying, adding that aviation fuel was found in the location where the fishermen found the debris.

Aji said no radio beacon signal had been detected from the 26-year-old plane. He said his agency was investigating why the plane’s emergency locator transmitter, or ELT, was not transmitting a signal that could confirm whether it had crashed.

“The satellite system owned by neighbouring Australia also did not pick up on the ELT signal from the missing plane,” Aji said.

Solihin, 22, a fisherman from Lancang Island, said he and two other fishermen heard an explosion around 30 metres from them.

“We thought it was a bomb or a tsunami since after that we saw the big splash from the water after the explosion. It was raining heavily and the weather was so bad. So it is difficult to see around clearly. But we can see the splash and a big wave after the sounds. We were very shocked and directly saw the plane debris and the fuel around our boat,” he said.

Sriwijaya Air President Director Jefferson Irwin Jauwena said the plane was airworthy. He told reporters that the plane had previously flown to Pontianak and Pangkal Pinang city on the same day.

“Maintenance report said everything went well and airworthy,” Jauwena told a news conference. He said the plane was delayed due to bad weather, not because of any damage.

It was raining at Jakarta’s Soekarno-Hatta International Airport when the plane took off for Pontianak, around 740 kilometres (460 miles) away.

Chicago-based Boeing said on its Twitter feed on Saturday that it was aware of the incident. It said it was closely monitoring the situation and “working to gather more information.”

The twin-engine, single aisle Boeing 737 is one of the world’s most popular planes for short and medium-haul flights. The 737-500 is a shorter version of the widely used 737 model. Airlines began using this type of plane in the 1990s, with production ending two decades ago.