Searchers are digging in the mud of a flooded mangrove swamp outside Bangkok for plane fragments and the remains of nine people believed to have been killed in a crash shortly after take-off.

Around 300 officers and rescue volunteers have been searching the crash site and will send any remains they recover for forensic identification, Chachoengsao province governor Chonlatee Yangtrong said late on Thursday.

Only small body parts had been recovered so far.

The crash site about 25 miles from Suvarnabhumi Airport was flooded after tides rose from a nearby river that flows into the Gulf of Thailand.

Video showed fragments of the plane in water in the middle of a wooded area. A rescuer worked in muddy water up to his chest.

Five Chinese tourists and four Thais, a pilot, co-pilot and two airline personnel, were on board the plane, provincial government spokesperson Sangdune Jewyu said.

The tourists were initially said to be from Hong Kong, but Hong Kong’s Immigration Department said on Friday they were not Hong Kong residents.

Photos posted on social media and Thai media websites showed all of their passports were issued in Shanghai.

Thai media, including the Bangkok Post newspaper, identified the Chinese victims as Zhang Jingjing, 12, Zhang Jing, 42, Tang Yu, 42, Yin Jinfeng, 45, and Yin Hang, 13.

The Civil Aviation Authority of Thailand said the turboprop Cessna Caravan C208B operated by the Thai Flying Service Company had departed at 2.46pm and air traffic control lost radio and radar contact 11 minutes later when the aircraft was about 22 miles south east of the airport.

It had been heading to Trat, a coastal province with beach resorts about 170 miles south east of Bangkok.

Authorities said the cause of the crash is not yet known, and an investigation is under way. The weather at the time of the flight was clear.

Pongthep Sirisawat of the Aircraft Accident Investigation Committee of Thailand said officials have recovered about 30% of the plane so far.

Because it had no black box and there are likely to be no survivors, it is necessary to collect as many pieces of the plane as possible to determine the cause of the accident, he said.