The Boeing 737-500, en route to Pontianak in West Kalimantan, lost contact shortly after taking off just after 2.30 pm (0730 GMT), a search and rescue official told local television.

There were 56 passengers on board, including 10 children, an official of the national search and rescue agency Basarnas said. Local media said there were six crew.

Reliable tracking service Flightradar24 said on its Twitter feed that Flight SJ182 "lost more than 10,000 feet of altitude in less than one minute, about 4 minutes after departure from Jakarta".

Agus Haryono, a rescue agency official, told Reuters that a search and rescue team had found debris suspected to be from the plane in the waters north of Jakarta, but it had not been confirmed that it was from the flight.

Sriwijaya Air, an Indonesian airline, said in a statement it is still gathering more detailed information regarding the flight before it can make a fuller statement.

A Boeing spokeswoman said, "We are aware of media reports from Jakarta, and are closely monitoring the situation. We are working to gather more information".

Surachman, a local government official, told Kompas TV that fishermen found what appeared to be the wreckage. Other channels showed pictures of suspected wreckage.

"We found some cables, a piece of jeans, and pieces of metal on the water," Zulkifli, a security official, told CNNIndonesia.com.

Nurhasan, a fisherman in the area known as Thousand Islands, told local media that he and his crew had found several pieces of metal.

The aircraft was 27 years old, according to registration details included in the Flightradar24 tracking data.

It was raining at Soekarno-Hatta International Airport at the time of take-off for Pontianak, around 740 km (460 miles) away.

Video images from the airport showed pictures of relatives of the passengers in tears as they awaited news of the fate of the aircraft.

A Boeing 737 MAX operated by Indonesian airline Lion Air crashed off Jakarta in late 2018, killing all 189 passengers and crew. The plane that lost contact on Saturday is a much older model.

SEARCH OPERATION

Rescue official Agus said 50 people were taking part in the search and that they would keep searching into the night.

Founded in 2003, Jakarta-based Sriwijaya Air group flies largely within Indonesia.

The airline has a solid safety record until now, with no onboard casualties in four incidents recorded on the Aviation Safety Network database, though a farmer was killed when a Boeing 737-200 left the runway in 2008 following a hydraulic problem.

The Boeing 737 is the world's most-sold family of aircraft and has undergone several makeovers since it entered service in 1968.

The 737-500 is two generations of development before the most recent 737 MAX, which has been embroiled in a worldwide safety crisis following crashes in Indonesia and Ethiopia. It does not use the software system implicated in those crashes.

Nonetheless, experts say planes such as Sriwijaya's leased 737-500 are being phased out for newer fuel-saving models. Civil jets typically have an economic life of 25 years, meaning they become too expensive to keep flying beyond that compared to younger models, but they are built to last longer.

(UPDATED)

JAKARTA: A Sriwijaya Air plane with more than 50 people on board lost contact after taking off from Indonesian capital Jakarta on Saturday en route to Pontianak in West Kalimantan province, local media reported.

Reliable tracking service Flightradar24 said on its Twitter feed that Flight SJ182 "lost more than 10,000 feet of altitude in less than one minute, about 4 minutes after departure from Jakarta".

Surachman, a local government official, told Kompas TV that fishermen found what appeared to be the wreckage of an aircraft in waters north of Jakarta and a search was underway. Other channels showed pictures of suspected wreckage.

"We found some cables, a piece of jeans, and pieces of metal on the water," Zulkifli, a security official, told CNNIndonesia.com.

The aircraft is a 27-year-old Boeing 737-500, according to registration details included in the Flightradar24 tracking data. It took off just after 2.30 p.m. (0730 GMT) and lost contact soon afterwards, a search and rescue official told local television.

Sriwijaya Air, an Indonesian airline, said in a statement it is still gathering more detailed information regarding the flight before it can make a fuller statement.

A Boeing 737 MAX operated by Indonesian airline Lion Air crashed off Jakarta in late 2018, killing all 189 passengers and crew. The plane that lost contact on Saturday is a much older model.

National search and rescue agency Basarnas said it could give no immediate comment.