ISLAMABAD, July 11 (Xinhua) -- A passenger bus fell into a gorge on Thursday morning in Attock district of Pakistan's eastern Punjab province, killing 13 people and leaving 30 others injured, police said.

The bus with 59 people on board fell into a gorge after skidding away from the superhighway near Hassan Abdal area of Attock district.

Police and rescue teams rushed to the site and shifted the bodies and wounded to two different hospitals.

The death toll might further rise as at least five of the injured were in critical condition, officials from the hospitals said.

The bus was heading towards the country's eastern city Lahore from northwest hilly city of Swat when the accident happened.

Police said that the accident took place due to careless and speedy driving at the wet and slippery road. However, a passenger who also got injured in the accident told local media that the bus driver was using a mobile phone, which was the main cause of the accident.