A Lion Air Boeing 737 passenger plane with 188 people on board has crashed into the sea shortly after taking off from the Indonesian capital, Jakarta.
Flight JT 610 was on a scheduled flight to Pangkal Pinang, the main town in the Bangka Belitung Islands.
It lost contact with ground control a few minutes after take-off, and was last tracked crossing the sea – it is unclear if there are any survivors.
The plane was a Boeing 737 MAX 8, a brand new type of aircraft.
Flight JT 610 took off from Jakarta at 06:20 local time on Monday morning (23:30 GMT on Sunday).
It was due to arrive at Depati Amir airport in Pangkal Pinang an hour later but about 13 minutes into the flight, authorities lost contact with the plane.
The pilot had earlier asked to return to Jakarta's Soekarno-Hatta airport, the head of Pangkal Pinang's search and rescue office, Danang Priandoko, told local news outlet Kompas.
At a news conference, officials said the plane had been carrying 178 adults, one infant and two babies, as well as two pilots and five cabin crew.
Image captionDistressed relatives are waiting for news at Depati airport in Pangkal Pinang
The head of Indonesia's disaster agency, Sutopo Purwo Nugroho, has tweeted images which he said showed debris and personal belongings that came from the aircraft and had been found floating in the sea.
End of Twitter post by @Sutopo_PN
He also shared a video he said had been taken from a tugboat off Karawang, just east of Jakarta, which appeared to show floating debris and an oil slick.
Debris was also seen near an offshore oil refinery operated by state-owned energy firm Pertamina, an official from the firm said
Image copyrightSUTOPO PURWO NUGROHO
Image captionSutopo Purwo Nugroho shared this image on Twitter, taken from the Pertamina facilities showing debris and oil
"The plane crashed into water about 30 to 40m deep," Search and Rescue Agency spokesman Yusuf Latif told AFP news agency. "We're still searching for the remains of the plane."
Lion Air Group's Chief Executive Edward Sirait earlier told Reuters: "We cannot give any comment at this moment. We are trying to collect all the information and data."
End of Twitter post by @flightradar24
The aircraft was reported to be a Boeing 737 MAX 8, a model only in commercial use since 2016. Flight tracking website Flightradar24 said the aircraft had been delivered to Lion Air in August.
Meant for short-haul travel, the single-aisle plane can fit a maximum of 210 passengers. The plane serving Lion Air flight JT 610 was configured to seat 189 passengers, said aviation consultant Gerry Soejatman.
He told the BBC the MAX 8 had been experiencing problems since it was introduced, including difficulties maintaining a level flight.
Indonesia, a vast archipelago, is heavily reliant on air travel, but many of its airlines have a poor safety record.
Lion Air is Indonesia's largest low-cost carrier, operating flights domestically as well as a number of international routes in South East Asia, Australia and the Middle East.
Established in 1999, it has had issues of safety and poor management in the past and was banned from flying into European airspace until 2016.
Image captionThis Lion Air plane landed in the sea off Bali in 2013, but all passengers and crew survived
In 2013, Lion Air flight 904 crashed into the sea on landing at Bali's Ngurah Rai International Airport. All 108 people on board survived. In 2004, flight 538 from Jakarta crashed and broke up on landing at Solo City, killing 25 people.
In 2011 and 2012 there was a spate of incidents where pilots were found in possession of methamphetamines, in one incident hours before a flight.