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An explosion near Fresno at about 2:30 p.m. halted north and south traffic on Highway 99, KCRA reports. Though southband lanes were reopened an hour later, northbound lanes remained closed. A rail line nearby was also interrupted.

The explosion took place at the Fresno County Sheriff's gun range. There, a work crew that included county jail inmates was using heavy equipment and appears to have hit a pipe carrying natural gas, according to a spokesman for the Fresno County Sheriff's Office. He said that one worker appeared to be in critical condition and that no law enforcement officers were injured.

A large fireball was seen by witnesses, and Pete Martinez of the Fresno Fire Department says that a two-alarm call for firefighters was put out. When PG&E crews turned off the gas line, firefighters quickly extinguished the flames.

Per a news release, a PG&E crew is at the scene and the incident is under investigation.

Last week, the Business Times reported that the PUC voted to penalize PG&E $1.6 billion for the 2010 San Bruno explosion that killed eight, meaning that total fines for that incident have reached $2.2 billion.

All SFist coverage of the San Bruno blast.

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