Map of the Philippines locating Baguio, where a bus plunged into a ravine Wednesday, killing at least 35 people. (AFP)

At least 35 people died while 12 others were seriously injured when the passenger bus they were riding in plunged into a deep ravine in Sablan town in Benguet province Wednesday morning, police officials said.

Senior Superintendent Agrimero Cruz, Jr., spokesman of the Philippine National Police (PNP), said six of the 12 injured victims are in critical condition and rest remain unconscious on the nearby hospital.

“The driver and the conductor of the bus were among those injured, they were rescued along with the rest of the injured passengers,” said Cruz in an interview.

Senior Superintendent Wilben Mayor, director of the Benguet Provincial Police Office, said the Eso passenger bus was travelling along a national highway from Baguio City to La Union when the incident occurred at around 9:30 a.m. at the vicinity of Barangay Banangan in Sablan town.

“According to the driver, it was a mechanical defect. He was trying to shift gear to slow down the vehicle but it would not work,” said Mayor in a phone interview.

“In the process, he lost control of the vehicle and then the accident happened,” Mayor added, noting that the driver might have faced difficulty controlling the vehicle since he was then negotiating a zig-zag road.

The official said the bus fell into a 35-feet ravine, adding that the bus travelling on high speed might have worsened the accident.

“All the 35 fatalities died on the spot, six of them suffered serious injuries,” said Mayor.

Mayor said that the driver was among those injured but was not among those in critical condition, adding that local investigators were able to interrogate him regarding the incident.

The bus conductor, on the other hand, sustained only minor injuries since he was able to jump out of the vehicle before it plunged into the ravine.

“Our main concern right now are the casualties, as of the moment, NP personnel and volunteers are undertaking rescue and retrieval operations,” said Mayor.