Eighteen people were killed when an explosion ripped through a minibus travelling in a militant-infested area of north-western Pakistan, police said.
There were conflicting reports as to whether the blast was caused by a bomb or by the gas cylinder used to power the vehicle.
The bus was travelling between the cities of Hangu and Kohat, which are close to Pakistan’s lawless tribal region.
The explosion tore apart the vehicle, killing all 17 people on board, and tipped over a second bus nearby, said Hangu police chief Abdur Rasheed.
One person on the bus which overturned was killed and 11 others were injured, he said.
Mr Rasheed said the explosion happened when the gas cylinder on board malfunctioned, but the top police official in the region said explosives were used to trigger the blast.
Islamist militants frequently carry out attacks in the area against both civilians and security forces.
Local television footage showed the twisted carcass of the first bus lying beside the road with little left except its wheels and undercarriage.
The second bus was on its side with its windows blown out and blood splattered across the outside.