An explosion which killed at least 11 people on a bus in the militant haven of north-western Pakistan was caused by a bomb, police say.
At least 10 others were wounded by the blast on the bus in Hangu district, Khyber Pakhtunkhwa province.
A bomb-disposal squad said the explosion had been caused by a remote-controlled device.
Police earlier had not ruled out the blast being a tragic accident caused by fuel containers on the vehicle.
Two exploded gas cylinders were spotted in the wreckage of the bus, which had been carrying 18 passengers from Hangu to nearby Kohat.
Police also revised the death toll from 15 to 11.
"The report of the bomb disposal squad shows that explosive materials fitted with a timer were placed near the gas cylinders which caused the explosion," district police chief Abdul Rashid told AFP news agency from the scene.
It is not clear why militants would want to attack a bus that was thought to be carrying civilians.
The BBC's M Ilyas Khan in Islamabad says there is speculation it could have been a sectarian attack targeting passengers from Pakistan's Shia Muslim minority.
The Taliban are engaged in a campaign of violence against security forces in Pakistan, carrying out attacks in revenge for US drone strikes on the tribal areas. Many civilians have been killed in the conflict. BBC News
