Crews were responding Wednesday afternoon to an underground electrical vault explosion believed to be caused by a nitrogen leak in a Southern California neighborhood.

The explosion was reported around 3:30 p.m. at Brynhurst Avenue and 63rd Street in the Hyde Park section of South Los Angeles, according to the Los Angeles Fire Department.

"It was a boom, like a big boom, like a car exploded," witness Nathaniel Arevalo said.

Authorities first cited a circuit failure as the cause of the explosion, but later discovered there was nitrogen running through the lines that carries the electrical wires underground.

They believe the nitrogen at some point leaked, creating prime conditions for an explosion.

Two manhole covers -- weighing hundreds of pounds -- appeared to be blown off. It tore entire sheets of concrete and asphalt 7 inches deep from the ground. It rained debris onto nearby vehicles, shattering windshields and damaging cars.

A large hole was left in the street following the explosion.

"They haven't seen anything like this and we haven't seen anything like this before," Kris Larson, Los Angeles Fire Department Battalion Chief, said.

The Los Angeles Police Department contacted the Los Angeles Department of Transportation to initiate street closures.

By 11 p.m. Wednesday, the Los Angeles Department of Water and Power were able to access the vault.

Crews completed repairs and paved the road as of 6:30 a.m. Thursday, reopening the road.

The lines that run under the street move 138,000 volts of electricity, which is enough to power more than a thousand homes.

No injuries were reported and the cause of the blast was under investigation.

"We got very lucky ... it's kind of a miracle," Larson said.