Islamabad: At least 13 people were killed on Wednesday when a worker struck a match to light a  cigarette at a gas cylinder shop and set off a series of explosions, a police official in the central Pakistani city of  Faisalabad said.

The incident happened while workers were re-filling gas cylinders for sale to domestic consumers.

The series of explosions caused the building to collapse.

"We have recovered nine bodies from the debris while four of the wounded died later in hospital," said Malik Yousaf, the
police official.

There were about two dozen people in the building and rescuers were still searching for anyone else who may have been  buried in rubble.