Tahir Hussain, commissioner of Faisalabad -- where the blast occurred -- called it an act of terrorism.
A large crater at the blast site suggested the explosion was caused by a device planted at the pump, he said. And when it went off, it triggered a second explosion at the gas station, he said.
The station is located close to several government buildings, he said. A building belonging to the intelligence agency was not damaged, but the offices of Pakistan International Airlines partially collapsed.
Hussain put the death toll at 15 and the number of wounded at 85, but said people were believed trapped under the rubble of the collapsed building.
Pakistan has the highest number of vehicles running on compressed natural gas (CNG) as well as the most refueling stations in the world, according to December 2009 figures from the International Association for Natural Gas Vehicles.
The New Zealand-based trade group placed the number of CNG stations in Pakistan at 3,068.