At least 19 people were killed after a bus heading to Philippines Capital Manila fell into a ravine on Tuesday evening.

The bus hit the railing of a bridge and plunged 15 metres off a cliff in the Occidental Mindoro province, police director Senior Superintendent Romie Estepa told the local DZMM radio station on Wednesday. Officials said the driver lost control, but added that it was unclear if the accident was caused by human or technical error.

Regional police spokesperson Imelda Tolentino told AFP that rescue workers were pulling out the dead and injured people from the vehicle. “The police are investigating why the driver lost control, and whether there was mechanical trouble or if the driver fell asleep,” she said.

Philippines’ poor public transportation regulations and bad roads make fatal highway accidents quite common in the country, Reuters reported.