LOS ANGELES — A March 26 explosion severely damaged the exterior of a branch belonging to $492 million Water and Power Community Credit Union, killing a firefighter the credit union says saved employees’ lives.

Linda Heidtke, director of marketing, said three credit union employees were on duty at the Westchester branch that day when thick clouds of smoke and series of small explosions attracted an armada of fire trucks and a crowd of onlookers. When credit union staff stepped outside to observe the excitement, fireman Brent A. Lovrein and another fireman, Anthony J. Guzman, quickly shooed them back inside.

Seconds later, the large explosion that killed Lovrein and severely injured Guzman detonated.

“In this instance, it was really clear that they saved our employees’ lives, and we’re extremely grateful,” Heidtke said.

In a press conference March 28, Los Angeles Mayor Antonio Villaraigosa called the explosion a freak accident, which began when an aging, 240-volt underground electric cable caught fire a half-block away at the corner of Sepulveda and La Tijera Boulevards, just south of Los Angeles International Airport. Smoke and gas spread underground to the credit union and other buildings nearby.

Lovrein was attempting to cut through the metal door of a utility room in the credit union building when sparks from his saw ignited gas that had built up in the room.

In response, Mayor Villaraigosa called for replacement of the city’s aging electrical infrastructure.

Heidtke said the inside of the branch sustained no damage, but the building’s exterior and power supply will take two to three weeks to repair. In the meantime, $1.4 billion Western Federal Credit Union has offered desk space in a nearby branch for displaced Water & Power employees, she said.

The explosion occurred shortly before Water and Power’s annual meeting, held at another location. The event prompted volunteers and attendees to pass a measure to immediately donate $5,000 in Lovrein’s memory.

The credit union has also set up a memorial fund for Lovrein through the Fire Family Foundation, a California charity. Both Water and Power Community and Los Angeles Fireman’s Credit Union are accepting donations from their members and the public.

Heidtke said the credit union effectively implemented its continuity plan after the disaster. Concerned members jammed up call center phone lines, but the credit union quickly posted information in its Web site, and sent an e-mail message to members.