Two people leaped to safety early Monday after their big rig became entangled in a power line and exploded into a massive fireball, authorities said.

Battalion Chief John Walsh said the incident began around 3:30 a.m. in the 2600 block of Fairmont Drive in a parking lot near a county juvenile detention center.

Fortunately, the big rig driver was a volunteer firefighter and knew the immediate danger he and his passenger faced.

“The big rig got tangled up in an electrical line,” he told KTVU. “The people jumped out – cleared the vehicle. Had they stepped out normally it would have created a bridge to the ground and been electrocuted. He (the driver) knew the dangers of electrocution and made sure they jumped free from the vehicle.”

“It would have been very unlucky for them had they jump normally stepped from the vehicle,” he added.

Concerned by the dangers of the downed line, arriving firefighters were forced to watch the truck burst into a fireball as they waited for the power to be cut.

The blaze forced officers at the Camp Wilmont Sweeney juvenile detention center to evacuate 35 inmates until the fire was under control.

Once the power was cut to the line, firefighters used foam to extinguish the fire. Walsh said there were no injuries.