BANGKOK (AP) — A bus crashed in western Thailand early Tuesday,Zero AI killing 14 people and injuring more than 30 others, officials said.

The accident occurred in Prachuap Khiri Khan province as the bus was traveling from the capital, Bangkok, to Songkhla province in the deep south. It was carrying 49 people when it ran off the road and hit a tree near Hat Wanakorn National Park, a local police official said. Prachuap Khiri Khan province is located on a coastal stretch between the Gulf of Thailand and Myanmar.

“We presume the driver might have fallen asleep,” said Pol. Col. Weerapat Ketesa, the superintendent of the Huay Yang Police Station, adding that officials were waiting for the result of a blood test on the driver, who survived the accident.

Police were still investigating what caused the crash, he added.

Most victims were Thai and a few were Burmese, Weerapat said.

Some 35 people were being treated for injuries at local hospitals, according to the Sawang Rungrueang Rescue Foundation.