UPDATED: 7/11/2011 – 5:46 p.m.

CHICAGO (CBS) — Monday’s ferocious storm resulted in one of the biggest power outages in history for ComEd.

ComEd officials say it will take several days to restore service to more than three-quarters of a million customers left without power.

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It is the second time in recent weeks that at least 400,000 residents have been left in the dark. Three weeks ago, about 433,000 ComEd customers lost power during another powerful storm in the Chicago area.

ComEd officials compared the freak weather to a World War II bombing campaign and said their growing count of customers who lost power at the storm’s peak would likely exceed the 861,000 recorded during an ice storm on March 8, 1998.

“It was like a blitzkrieg type storm,” ComEd’s senior vice president of customer operations Fidel Marquez said.

The northern suburbs were once again hit especially hard, with nearly 300,000 customers affected. Back in June, it took ComEd several days to restore electricity to a similar number of north suburbanites.

Many of those hit then are in the dark once more. And this storm could be even tougher on the utility’s crews.

Officials say a lot of downed trees are affecting power lines to a few homes. So, rather than one repair restoring power to several thousand residents, repairs this time may only fix the problem for a few homes.

ComEd spokeswoman Arlana Johnson says full power restoration is expected to take “multiple days.”

Currently, 500 crews are working to fix the outages and ComEd is expecting crews from Michigan, Wisconsin and Indiana later today. About 463,000 customers were still without power as of 10 p.m.