A fireball injured at least 11 people and temporarily closed down Highway 99 after a tractor operator accidentally punctured the 12-inch natural gas pipeline, authorities said.

Eleven victims were transported to hospitals, where officials said four were in critical condition, two were in serious condition and the remainder suffered minor injuries.

The explosion, which sent flames surging past the tops of nearby trees, happened on a shooting range close to busy Highway 99, one of the San Joaquin Valley’s two main freeways.

The tractor was being operated by a county public works employee who was using it to reinforce a berm behind the targets at the Fresno County Peace Officers' Range, according to a spokesman withthe Fresno County Sheriff’s Office.

Source: SF Gate  http://www.sfgate.com