The failure of a key transmission line was blamed for power outages that left nearly half a million people without air conditioning for about 30 minutes on a day when temperatures in Southern California hovered around 100 degrees.

Southern California Edison (search) began shutting off power in areas Thursday after the California Independent System Operator (search), which operates the electric grid in California, declared a transmission emergency.

About a half hour later, power was being restored to people subjected to the blackouts in Fontana, La Puente, Cathedral City, Huntington Beach, Long Beach and Ontario, said ISO spokeswoman Stephanie McCorkle.

Few problems were reported in communities struck by the blackouts, officials said.

The utility scattered the outages to those points east and south of Los Angeles. If the problem had persisted, officials said they would have shifted the blackouts to other areas on a rotating basis.

The outages were a reminder of the energy crisis that struck California in 2000 and 2001 when the state suffered several rolling blackouts amid limited power supplies.

Gov. Arnold Schwarzenegger (search) quickly huddled with electricity grid managers after Thursday's blackouts, saying later the state has enough power for the summer.

Schwarzenegger ousted former Gov. Gray Davis (search) in a 2003 midterm recall election after Davis' delayed response to the energy crisis left him politically vulnerable. He said Thursday his administration inherited an outdated energy system and the blackouts show the state needs a comprehensive energy program.

Schwarzenegger's proposal to reorganize California's energy agencies under a new Cabinet-level secretary of energy was rejected by the state Senate on Thursday, with critics saying it violated the California Constitution.

Schwarzenegger said he would meet with legislative leaders in an effort to reach a compromise, but a spokesman said a second attempt at passage was unlikely before next year.

Temperatures around 100 degrees in inland areas created increased power demands Thursday, officials said. But the situation did not turn into an emergency until the sudden loss of a key transmission line from the Pacific Northwest, McCorkle said.

A transformer in Los Angeles' Sylmar section that converts power from the Pacific Northwest took itself off-line automatically Thursday afternoon when an oil flow alarm went off, said Carol Tucker, a spokeswoman for the Los Angeles Department of Water and Power (search), which co-owns the transmission line.

The converter station was returned to half capacity Thursday night.