At least 20 people were killed and 21 others injured when a passenger bus skidded off a mountainous terrain and plunged into a ravine in northwest Pakistan’s Gilgit Baltistan region on Friday, authorities said.

The incident occurred around 5:30 am on the Karakoram Highway in Diamer district when the bus was on its way from Rawalpindi to Hunza, a police official said.

The driver lost control of the vehicle which then overturned and landed near the banks of the Indus River, the official said. As many as 43 passengers were aboard the bus when the incident took place, the official said. The injured were moved to the Chilas hospital, the official said. The official said the rescue efforts assisted by army helicopters were over and the dead and injured were moved to the hospital. The source said the death toll was expected to rise further as many of the injured were in critical condition. Gilgit Baltistan Chief Minister Haji Gulbar Khan expressed condolences over the incident and directed the administration to provide immediate medical aid to the injured. Giltgit-Baltistan government spokesperson Faizullah Faraq said an emergency was declared at the Chilas Hospital after the accident. Prime Minister Shehbaz Sharif expressed grief on the loss of lives and conveyed his sympathies to the bereaved families. He instructed authorities to provide the injured with “every possible medical treatment”. Interior Minister Mohsin Naqvi also expressed his condolences on the incident and prayed for the speedy recovery of the injured.