Story highlights The bus was carrying at least 70 government employees

A remote-controlled explosive device destroyed the vehicle, police say

An eyewitness describes seeing passengers thrown into nearby fields by the blast

At least 17 people were killed and more than 30 others wounded in an explosion that ripped through a bus carrying government employees in northwest Pakistan on Friday, authorities said.

The blast destroyed the bus, police said. It was carrying at least 70 employees of various departments of the secretariat of Peshawar, the capital of the volatile province of Khyber Pakhtunkhwa.

Police think the explosion was caused by a remote-controlled device planted in a tin can containing about 6 to 8 kilograms (13 to 18 pounds) of explosives, said Nasir Durrani, inspector general of police in the province.

No group has so far claimed responsibility for the attack.

Hakim Khan, an eyewitness, said the explosion hurled people sitting on the bus's roof out into fields by the side of the road.

Authorities said 34 people who were wounded in the blast are being treated at nearby hospitals.

Sikander Khan Sherpao, senior minister of Khyber Pakhtunkhwa, suggested the attack had been carried out by forces wanting to sabotage recent efforts by the national government to pursue peace talks with the Pakistani Taliban.

Violence is frequent in Peshawar and the surrounding region.