Ships and planes were scouring the coast of southern Myanmar on Wednesday after a military aircraft vanished over the Andaman Sea with 120 soldiers, family members and crew on board, the army and civil aviation officials said.

The Chinese-made Y-8-200F transport plane left the coastal town of Myeik at 1:06 p.m (0636 GMT), heading north to Myanmar’s largest city of Yangon on a regular weekly military flight that stops at several coastal towns along the way, officials said.

The plane lost contact 29 minutes after take-off while flying at 18,000 feet (5,485 meters) over the sea, about 43 miles (70 km) west of the town of Dawei, the military said.

“We don’t know what exactly happened to this plane after the loss of contact,” said Kyaw Kyaw Htey, a civil aviation official at Myeik airport.

Civil aviation authorities initially said there were 105 people onboard. The military later said those on board included 106 soldiers and their family members and 14 crew. The maximum capacity of the aircraft was 200 people, said a military officer.

Reuters