Copyright 2009 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

By Daisy Nguyen
The Associated Press

LOS ANGELES — A fire in an aging high-voltage cable caused a series of blasts and led to the death of a firefighter as he investigated the explosions, city authorities said Friday.

Mayor Antonio Villaraigosa called it "a freak accident" and focused attention on the electrical infrastructure of the nation's second-largest city. The cable was about 60 years old.

The blasts, which blew covers off of manholes, also badly injured a fire engineer and damaged a credit union building.

Firefighter Brent A. Lovrien, 35, was killed Wednesday when he turned on a power saw to cut through the metal door of a utility room that had filled with smoke from the cable fire. The saw ignited gases that had built up in the room, triggering the blast that killed him, authorities said.

The initial fire started in a 240-volt underground cable below a busy corridor near Los Angeles International Airport, said Battalion Chief John Miller, head of the Fire Department's arson and anti-terrorism section. Witnesses reported smelling smoke in the area four hours before the explosions.

Smoke from the fire built pressure which led to an explosion that blew a manhole cover near an office supply store, Miller said. Witnesses reported seeing the cover fly more than 20 feet.

The smoke traveled half a block to the Water and Power Community Credit Union building where it created a second explosion on a street corner, leaving another manhole cover slightly ajar. As firefighters were investigating the second explosion they received reports of smoke coming from the utility room at the rear of the building.

The high-voltage copper cable in a conduit made of lead was degraded, said David Nahai, chief executive officer and general manager of the Los Angeles Department of Water and Power.

He said the tragedy was a reminder that the city needs to aggressively replace old cables with modern ones that have synthetic coverings.

"The infrastructure is starting to show its years and we have to move forward to replace it as fast as we can," he said.

The cause of the cable fire remains under investigation, but Nahai said it was possible there was an "overloading on the copper."

Fire Engineer Anthony J. Guzman, 48, was in serious but stable condition after surgery, Fire Chief Douglas Barry said.