At least 24 people were killed Tuesday when a passenger bus plunged into a ravine in the northern Philippines, a local police officer said.

The accident occurred in a remote village in Carranglan town in Nueva Ecija province, about 150 kilometres north of Manila, according to senior police official Robert de Guzman.

De Guzman said bystanders saw the speeding bus fell into the ravine, over 100-metres high, in the village of Capitantalan.

Investigators were still determining the cause of the accident, he added.

The rest of the estimated 45 passengers were plucked by rescuers who struggled with ropes to descend down the ravine to reach the bus wreckage in Nueva Ecija province's Carranglan town, disaster-response officer Mark Raymond Cano told The Associated Press.

Many of the passengers had serious injuries and were taken to a hospital, he said.

Poorly maintained passenger buses, inadequate road safety features and weak enforcement of local transport laws have been blamed for many vehicular accidents.

In February, a sightseeing bus carrying college students on a camping trip lost its brakes on a steep downhill road and smashed into a concrete electrical post in Tanay town in Rizal province east of Manila, leaving 15 people dead.