BANGKOK (AP) — Search crews dug through the mud of a flooded mangrove swamp outside Bangkok on Friday for plane parts and the remains of the five Chinese passengers and four Thai crew members who were believed to have died in a crash shortly after takeoff.

About 300 officials and volunteer rescue workers have searched the crash site and will send any remains they can recover for forensic identification, Chonlatee Yangtrong, governor of Chachoengsao province, said late Thursday. So far, only small body parts have been recovered.

The crash site, about 40 kilometers from Suvarnabhumi airport, was flooded by a nearby river that flows into the Gulf of Thailand. A video showed debris from the plane floating in the water in the middle of a forest. A rescue worker was working chest-deep in muddy water.

On board the plane were five Chinese tourists and four Thai nationals, a pilot, a co-pilot and two airline service staff, said provincial government spokesman Sangdune Jewyu.

The tourists are believed to be originally from Hong Kong, but Hong Kong’s immigration authorities said on Friday that they were not Hong Kong residents. Photos posted on social media and Thai media websites showed that all of their passports had been 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 Thai Flying Service Company’s Cessna Caravan C208B turboprop aircraft took off at 2:46 p.m. and that air traffic control lost radio and radar contact with the aircraft 11 minutes later when it was about 35 kilometers southeast of the airport.

The destination was Trat, a coastal province with seaside resorts about 275 kilometers southeast of Bangkok.

The cause of the crash is not yet known, the authorities said. The investigation is ongoing. The weather was clear at the time of the flight.

Pongthep Sirisawat of Thailand’s Aircraft Accident Investigation Committee said they had recovered about 30 percent of the plane so far. Since the plane had no flight recorder and there are probably no survivors, it is necessary to recover as many parts of the plane as possible to determine the cause of the accident, he said.