Rescuers and fire fighting vehicles are seen at the vessel explosion site in Pingtan, Southeast China's Fujian province, July 26, 2011. Twelve people including four fire fighters were injured, after an explosion on a 5,000-tonne cargo vessel caused fire Monday night at a shipyard at Pingtan Island. An initial investigation has found the explosion was triggered by gas cutting used by repair workers.  [Photo/Xinhua]

Twelve people including four fire fighters were injured, after an explosion on a 5,000-tonne cargo vessel caused fire Monday night at a shipyard at Pingtan Island, southeast China's Fujian Province.

The injured have been sent to hospital, and nine of them suffered severe injuries, according to the Fuzhou fire department Tuesday.

Fire fighters contained the fire about three hours after the blast happened at 8:35 p.m. Monday.

There were 21 crew on board the Tianjin-registered vessel, which was being examined and repaired at Kan'ao Shipyard, Su'ao dock of Pingtan Island, at the time of the accident.

The rescue operation was obstructed by successive blasts, after rescuers braved the fire to pull out 20 crew members and removed combustible oxygen tanks and gas pitchers. Four fire fighters were injured in the blasts. But fire fighters continued the rescue and pulled out the last crew.

An initial investigation has found the explosion was triggered by gas cutting used by repair workers.