SAN LEANDRO -- A volunteer firefighter and another man escaped with their lives early Monday morning after the big rig they were in ran into live electrical wires, sparking a blaze that engulfed the vehicle.

The two men "jumped for their lives" after the truck struck the wires around 3:30 a.m. near the Camp Sweeney juvenile probation facility at 2600 Fairmont Drive, Battalion Chief John Walsh from Alameda County Fire said. It was unclear if the wires were hanging low or why they may have been in the truck's path, Walsh said.

The driver is a volunteer for Solano County Fire, Walsh said, and "he realized right away that the possibility for electrocution was there, and that they would have to jump free of the vehicle. His experience and training were a big reason they were able to escape."

Fire crews chose not to attack the fire immediately, instead allowing it initially to consume the truck. According to Alameda County spokeswoman Aisha Knowles, the truck belonged to the California Prison Authority and was used to pick up and deliver laundry from Camp Sweeney twice a week.

"With both occupants out of the vehicle, and the chance for electrocution with the live wires, it was better to wait to shut the power (to the wires) down," Walsh said. "If someone had been trapped in the vehicle, we would've been much more aggressive in our approach."

Thirty-five people at the Camp Sweeney facility were evacuated as a precaution. Camp Sweeney is an unlocked 24-hour residential program that part of Alameda County's Juvenile Hall.

Crews from Alameda County Fire and PG&E were investigating. No residents lost power as a result of the wreck, Alameda County Fire spokeswoman Aisha Knowles said.

Rick Hurd covers public safety. Contact him in Walnut Creek at 925-945-4780 and follow him at Twitter.com/3rdERH.