The roof of?a cleaning firm's dormitory building is blown up by a gas cylinder explosion in Qingdao, Shandong province, Dec 4, 2013. [Photo/Icpress.cn]

A mother and her two sons, one of them aged 9, were injured in a gas cylinder explosion in Qingdao, Shandong province, on Wednesday and were rushed to a hospital for treatment.

Firefighters said the accident was caused by a leaking cylinder.

They removed three gas cylinders from a cleaning firm's dormitory building, where the blast took place. China News Service said the accident happened at 7 am and the family was living in the dormitory.

At 11 am, the gas supply to nearby areas was suspended for underground pipelines to be inspected, the report said.

The building, which is only 50 meters from a kindergarten, acted as a garbage transfer station before becoming a dormitory for cleaners.