BANGKOK: At least 29 people were killed and four badly injured when a bus plunged into a deep ravine in northeast Thailand, police said Friday.

The accident occurred around midnight Thursday-Friday in Lom Sak district, Phetchabun province while the bus was en route to the northern province of Chiang Rai.

“We suspect the bus driver fell asleep,” Major General Sukit Samana, police commander of Phetchabun province, told AFP.

“We found 28 bodies in the ravine, which is about 30 metres (100 feet) deep. And one died at the hospital,” he said.

Four others were in a critical condition.

“The eyewitness who informed the police said the bus went very fast before it plunged into the ravine,” he said.

The bus, which was carrying 40 passengers, was completely destroyed in the accident.

The accident occurred as millions of Thai motorists are expected to travel during the New Year holidays.

Deadly road accidents are common in Thailand.

At least 20 people were killed in October when a tour bus carrying elderly Buddhist devotees plunged into a ravine in northeast Thailand.

A recent report by the World Health Organisation said the country saw some 38.1 road deaths per 100,000 of population, compared to an average of 18.5 in Southeast Asia as a whole.