CEBU, Philippines — A tourist bus packed with Iranian nationals plunged into a ravine Sunday while negotiating a mountain road in the central Philippines, killing at least 18 people and injuring more than 30 others.

The bus, carrying dozens of mostly Iranian medical students and doctors, apparently suffered brake failure then plummeted into a 100-foot (30-meter) ravine in Balamban town in Cebu province, police Senior Superintendent Erson Digal said.

At least 18 people, mostly Iranians and including children, were killed, said regional military spokesman Lt. Col. Wilson Feria, who was at the scene of the accident.

Villagers and police pulled at least 10 bodies from the mangled bus wreckage at the rocky bottom of the ravine. Several seriously injured passengers were brought to hospitals, Digal told The Associated Press.

Feria said at least seven passengers later died in hospitals.

Many of the Iranian victims were medical students in Cebu, a bustling commercial and tourism center 350 miles (560 kilometers) southeast of Manila. They were identified by relatives and through their IDs, Digal said.

Feria said it was not clear if the Iranians, who rented the bus, were involved in a medical mission or went for an outing at one of several resorts in and around Cebu.

He said four air force helicopters ferried the dead and at least 31 injured passengers to a military camp in Cebu city, where they were picked up by ambulance vans then brought to hospitals.

An unspecified number of passengers were still pinned in the wreckage, Digal said.

A Japanese shipbuilding company in Balamban offered to send a crane to help lift the bus so those pinned underneath and in the wreckage can be retrieved, Feria said.

Poorly maintained vehicles and roads, along with inadequate safety signs, railings, training and weak traffic law enforcement, are blamed for many deadly accidents in the Philippines.