According to reports, the explosion went off in a bank building in the Sher Shah area and social media and TV footage showed the two-floor structure's windows and doors blown out, with documents scattered across a wide area.
Cars and motorcycles parked nearby were also damaged.
Provincial police told AFP a bomb disposal squad was investigating, but "apparently the leakage of gas was the cause", reported NDTV.
The report further stated that 12 people had been confirmed killed, and 13 were being treated for injuries in the blast in Pakistan.