Nineteen people were killed and 21 others injured when a bus veered off the road and plunged down a ravine in the central Philippines, police said Wednesday.

The bus was heading to the capital Manila when it crashed through the railing of a bridge on Mindoro island late Tuesday, said regional police spokeswoman Imelda Tolentino.

‘The survivors said the driver lost control of the vehicle and that is why it fell,’ she told AFP.

‘Police are investigating why the driver lost control -- whether there was mechanical trouble or the driver fell asleep,’ she said.

The bus driver was among the deceased, she added.

Police photos showed rescue workers clambering down the cliff to reach the bus, which lay on its side amongst trees and grass about 15 metres (49 feet) below the road.

The accident occurred near Sablayan town, which is about 195 kilometres (121 miles) south of Manila.

Road accidents are common in the Philippines, where inadequately maintained buses and poorly trained drivers form the backbone of land transport options.

In 2010, 41 people died, including five foreigners, when a packed bus plunged into a deep ravine in the northern Philippines.

Another 31 people perished in bus crash in the country's north in April last year while 20 were killed when two buses collided in the north in December.

Public transport regulators on Wednesday suspended the bus company involved in the Mindoro crash and said they would be inspecting its facilities.

Senator Grace Poe took aim at the nation's regulation system, saying ‘vehicles that are not roadworthy or even those we label as rolling coffins are still allowed to ply the roads with near impunity.’