The government has launched an audit into the state power monopoly and distributor to find out the exact cause of this week's massive blackouts that left millions of homes without electricity for hours, officials said Saturday.

Massive blackouts occurred on Thursday as unseasonal heat waves raised electricity demand, forcing authorities to cut power without prior warning. More than 2 million homes and numerous businesses suffered until the problem was resolved five hours later.

A preliminary probe showed that a wrong demand forecast for electricity was blamed for the unprecedented accident.

The Ministry of Knowledge Economy, which handles energy affairs, said that it has kicked off a two-day audit into the Korea Power Exchange (KPX) and the Korea Electric Power Corp. (KEPCO) to determine the exact cause of the accident.

The investigation is part of government efforts to draw up measures to prevent the recurrence of a similar accident in the future, it said.

President Lee Myung-bak harshly rebuked electricity officials Friday during a visit to KEPCO's head office in southern Seoul.

Opposition parties demanded that Knowledge Economy Minister Choi Joong-kyung resign to take responsibility for the power outages.

"The recent power outages stemmed from the government's lack of management capacity," said Lee Yong-sup, a spokesman for the main opposition Democratic Party.

There was no immediate response from the knowledge economy minister to the opposition demand. Ministry officials said Choi plans to unveil steps to prevent the recurrence of such an accident on Sunday. (Yonhap News)