Toll from Pakistan ammunition store blast rises to 17

Gandapur told Reuters that experts had visited the spot but did not find any evidence of a militant attack. Another police officer had said after the blasts that ammunition caught fire, likely from an electrical short circuit.

Swat was previously long controlled by Islamist militants before they were flushed out in a military operation in 2009.

Pakistani police and military have a significant presence in the valley.

Pakistan has seen a rise in attacks by Islamist militants in the last few months, particularly since negotiations with the Tehreek-e-Taliban, an Islamist militant group, broke down last year.

Earlier this month, Pakistan announced a new nationwide operation to root out militancy.