FRESNO, Calif. -- A large gas pipeline exploded into a tower of fire Friday in Central California, closing both directions of a major highway in the region and injuring at least 15 people, four of them critically, authorities said.
It was not clear what caused the explosion at the Fresno County Sheriff's gun range that brought traffic in the area to a halt. But authorities say it occurred while a county equipment operator was working with a jail inmate crew to expand a road on the range alongside heavily travelled Highway 99.
The flames shot well over 100 feet into the air, several witnesses said.
Four patients were being treated at Community Regional Medical Center's burn and trauma unit, spokeswoman Mary Lisa Russell said. Three of them are in critical condition and one is in serious condition, she said.
Four other patients were taken to St. Agnes Hospital and three more to Madera Community Hospital, and four others were treated and released at the scene, Fresno County Medical Services director Dan Lynch said.
Traffic heading north and south on Highway 99 in Fresno was halted by the explosion about 2:30 p.m. as flames towered over the roadway, the California Highway Patrol reported. The highway was reopened three hours later, the CHP said.
The explosion happened at the Fresno County Sheriff's gun range, where a work crew, including county jail inmates, using heavy equipment apparently hit a Pacific Gas & Electric Co. pipe carrying natural gas, Fresno County Sheriff Margaret Mims said.
A nearby rail line was also halted out of concern that a passing train could spark leaking gas.
The front-loader driver was a county public works employee who had been working at the shooting range all day, along with 13 jail inmate workers. They were expanding a road on a tall berm that confines gunfire to the range, Mims said.
Four inmate workers are among the injured, she added.
Asked whether the driver was scraping or digging the earth when the gas exploded, Mims said her office is investigating. "Hopefully we'll be able to speak to the worker to see what action he was taking at the time," she said.
The flames prompted a two-alarm call of firefighters, said Pete Martinez of the Fresno Fire Department.
The 12-inch diameter pipeline involved in the fire belongs to PG&E, Martinez said. A front-loader was in the area, but it's unclear if the vehicle was digging at the time of the explosion. The operator was flown by helicopter to a hospital in serious condition, Martinez said.
"It was a large explosion that shook the surrounding area," he said.
PG&E spokesman Keith Stephens referred questions to local authorities. Stephens said he could not comment on whether the pipeline involved was PG&E's or whether anyone with PG&E had been at the scene.
"Our thoughts and prayers are with those who are reported to be injured. We do not have definitive information" on the situation, he said.
PG&E's natural-gas operations have been under intensifying scrutiny in the wake of a fiery 2010 PG&E pipeline blast that killed eight people in the San Francisco suburb of San Bruno.
National Transportation Safety Board investigators blamed faulty safety practices by PG&E, and lax oversight by state regulators, for the 2010 blast.
Earlier this month, state regulators levelled the state's biggest-ever penalty against a utility -- $1.6 billion -- against PG&E for the San Bruno blast. California Public Utilities Commission President Michael Picker said at the time that continuing safety citations against the utility made him doubt that the utility had embraced a culture of safety, and he raised the possibility of breaking apart the utility's gas and electric operations.
