UPDATE: Electrical Explosion Buckles Monrovia Street, Forces Evacuation of World Vision

Authorities ordered the evacuation of businesses along a stretch of Chestnut Avenue Thursday morning after an underground electrical explosion buckled a portion of the street.

The explosion blew a hole through the asphalt on Chestnut between Fifth Avenue and Monterey Avenue. The cause of the explosion was not immediately clear.

The headquarters for World Vision were briefly evacuated after the explosion, reported at 8:35 a.m., but employees were let back in shortly thereafter, city spokeswoman Jennifer McLain said. Nearby residences were not evacuated, she said.

David Song, a spokesman for Southern California Edison, said the company is investigating what happened and attributed the explosion to equipment failure.

"It's failed underground equipment, that's all we know right now," Song said.

The explosion knocked out power for 98 customers in the area but power was restored within an hour, Song said.

Chestnut remains closed to traffic from Fifth to Monterey. Edison crews are on scene to assess the problem.

Check back later for more on this breaking story.