A truck veered off a downhill mountain road and plunged into a ravine in the central Philippines, killing nine workers on board, police said.

The workers were traveling back to their office after delivering crude oil and other supplies in a farming village in Bayawan city in Negros Oriental province when their truck overshot the road and fell into a 30-meter- (98-foot-) deep ravine, police said. It was loaded with five drums of crude oil.

The cause of the accident, which happened shortly before noon in good weather, was not immediately clear. The workers died while being brought to a hospital, provincial police chief Col. Timmar Alam said.

The Philippines has a disturbing record of deadly road accidents, which are often blamed on weak enforcement of traffic laws, reckless driving, rickety vehicles and inadequate road safety railings and signs.