At least 17 passengers were killed and a woman injured when a passenger bus fell into a deep gorge on Sunday evening while travelling on the Karakoram Highway in Kohistan's Lotar area, DawnNewsTV reported.

According to police officials, the bus was headed to Rawalpindi from Gilgit Baltistan's Ghizer area, of which most of the deceased were residents.

Upper Kohistan District Police Officer Abdul Ghafoor accompanied by a police team reached the spot after receiving word from people who had begun rescue operations to retrieve the dead bodies.

The police official told DawnNewsTV that due to the non-availability of any mobile network they were facing communication problems.

An eyewitness, Sharif Khan, said that the incident took place in the evening and it was only until much later that he received mobile signals and was able to inform the police.

Khan said there are very few houses in the area and the men, however few in number, were making efforts to retrieve the people but due to the darkness and rugged terrain of the mountainous area, they were facing tremendous challenges.

According to other eyewitnesses, the injured woman did not receive any major injuries and was taken to a home nearby. She spoke in a language none of the residents of Kohistan could understand as she belonged to Ghizer.

As the night progressed, police officials confirmed that bodies of all 17 deceased had been retrieved from the ravine but warned that the death toll could rise as rescue operations were still underway to ascertain if there are any bodies remaining.

Meanwhile, ambulances and private vehicles had been dispatched to the site, police said, adding that since the site is in a far-off location, it will be some time before the bodies are collected.

An emergency was declared in the Dasu rural health centre in Upper Kohistan as news of the accident spread throughout the district.

The cause of the accident remains unknown so far.

In September a woman tourist was killed and three others were injured when a landslide hit a van on the Karakoram Highway near Attabad Lake in Hunza district.

According to area residents, the portion of Karakoram Highway where the accident occurred had become dangerous as frequent landslides from mountains hit vehicles.

In another incident which occurred in December last year, three military personnel were killed and two others suffered critical injuries when their car plunged into a deep ravine near Pattan area in Bisham on the Karakoram Highway

The ill-fated car was going to from Gilgit to Rawalpindi as the soldiers were returning to their homes during vacations, local police officials had said.