BANGKOK: At least 30 people died and more than 20 were injured when a bus careered off a hillside road and into a ravine in northern Thailand, authorities said Tuesday, updating the official toll.

The accident took place at about 8:40 pm (1340 GMT) on Monday in Tak, which borders Myanmar, as several buses ferried Thai local government workers for a field trip to Laos.

“The latest death toll from the accident is 30 — nine men and 21 women,”said Suriya Prasartbandid, the governor of the western province of Tak.

Twenty-two others were injured, he told AFP.

“The bus was totally destroyed. Its engine fell out and we're waiting for heavy machinery to lift the wreckage,” Suriya said.

He said there were more than 300 accidents on the same road last year.

Thailand's roads are among the world's deadliest and accidents are common, especially on buses travelling late at night.

“The brakes failed as the bus came downhill on a hilly road and it crashed through the concrete barrier and fell into a 150-metre (500-feet) deep ravine,” a local police captain, Sittichai Panyasong, said by telephone.

The victims are mainly believed to be local government officials, but a child was also among the injured, he said.

A recent report by the World Health Organization said Thailand saw 38.1 road deaths per 100,000 people in 2010 -- behind only the Dominican Republic in the Caribbean and the South Pacific island of Niue.

That compares with an average of 18.5 per 100,000 in Southeast Asia as a whole.

At least 13 schoolchildren died last month when their bus collided with a truck on a trip to the coast south of Bangkok.

The students, aged around 10 to 14 years old, were heading to the resort city of Pattaya from the northeastern province of Nakhon Ratchasima.

Officials say roughly 60 percent of traffic accidents in Thailand are caused by human error, with poor road and vehicle conditions posing additional hazards. Alcohol also plays a significant role.

Those who cannot afford to fly have little choice but to use the roads in country where the rail infrastructure remains weak.

Bus operators are required to provide seat belts but passengers are not legally obliged to use them.

In December, dozens of people were killed when a bus carrying New Year travellers plunged off one of Thailand's highest bridges in the kingdom's northeast.

At least 20 people were killed in October when a tour bus carrying elderly Buddhist devotees fell into a ravine, also in the northeast.