LOS ANGELES -- Authorities said one firefighter was killed and another remained hospitalized Wednesday evening in critical condition after an explosion at a building near LAX.

Video: Firefighter Killed In Explosion Near LAX
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Fire officials said the firefighters were transported to the hospital in critical condition. Fire officials announced at an afternoon news conference that one firefighter died. The firefighter, a 10-year veteran of the department, was not identified.

Officials said the second firefighter was in critical but stable condition. A bystander was treated and released, according to fire officials.

The explosion happened at the southwest corner of Sepulveda Boulevard and La Tijera Boulevard, at 8800 Sepulveda Boulevard.

Authorities said the blast appeared to be "electrical in nature." Deputy Chief Mario Rueda of the city fire department said the explosion was in an electrical vault.

Firefighters were called to the location to investigate dislodged manhole covers. During the investigation, firefighters said they noticed smoke coming from a room near the back of a building and several explosions occurred in the room, according to fire officials.

Video from news helicopters showed damage to a credit union for Department of Water and Power employees. At the Wednesday afternoon news conference, fire officials said a room at the back of the building where the blast occurred housed an electrical panel.

Fire officials said there was no indication on the outside of the door to indicate it contained electrical equipment.

Sepulveda Boulevard was closed during the investigation.

Spokeswoman Offers Alternate Routes

An LAX spokeswoman said Wednesday evening traffic on Sepulveda Boulevard between Manchester and Century boulevards was blocked because of the explosion earlier in the day.

Nancy Castles said motorists should avoid Lincoln Boulevard adjacent to the airport until further notice because traffic is blocked on northbound Lincoln and Sepulveda and very congested on the southbound portion of Lincoln.

She recommended the following routes for passengers and motorists en route to the airport:

• from north of LAX: take the San Diego (405) Freeway to westbound Century Boulevard; or take the 405 to Manchester Boulevard to Aviation Boulevard to Century Boulevard; or use Pershing Drive on the west side of the airport. Avoid Lincoln and take Culver Boulevard or Manchester Boulevard to Pershing Drive.
• From east of LAX: take the Glenn Anderson (105) Freeway east to northbound Sepulveda Boulevard through the Sepulveda Tunnel, which remains open for airport traffic only and for motorists headed east on Century.
• From south of the airport: remember that northbound Sepulveda remains open through the tunnel.