Tens of thousands of New Yorkers were still without power Friday, the fifth day of a mysterious electrical problem that has been blamed for subway delays, flight cancellations and dead air conditioners during the hottest week of the year.

Power company Con Edison initially said fewer than 2,000 customers were affected, but it increased that number tenfold Friday morning to 25,000 customers.

Mayor Michael Bloomberg estimated that would translate to about 100,000 people considering that each "customer" could be more than one household in an area where homes are often sectioned into multiple units, and could even be an entire apartment building.

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"The sad thing is, this shouldn't have happened," Bloomberg said. "We don't know why, but the most important thing -- make sure nobody dies or gets hurt and then help Con Ed to get it back up."

Queens District Attorney Richard Brown issued a statement Friday saying his staff was conducting a review to determine if criminal charges are warranted.

The blackouts started Monday in a handful of neighborhoods in Queens. Two LaGuardia Airport terminals lost power Monday night and again on Tuesday.

Since then, hundreds of businesses have since been idle, and the city's jail complex on Rikers Island has had to operate on backup generators. Some building's elevators were not running, and traffic lights at some intersections were not working.

"This is outrageous," City Councilman Peter F. Vallone Jr. said. "When is this going to be fixed? If it's going to be days, they should tell people it is going to be days."

The blackouts were at their worst on Wednesday, when 10 of the 22 feeder cables that supply the area with power were down simultaneously. The temperature had hit 100 degrees in the neighborhood the day before.

Consolidated Edison spokesman Chris Olert said the revised number followed a block-by-block cable inspection in northwest Queens on Thursday night. It said previous estimates came from the number of customers who called to complain.

Olert said the power company was making every effort to get the situation fixed but couldn't estimate when that might happen. He said the company didn't know why things went wrong.

"Chances are fair, but not firm, that it was heat related, but right now that is just a hypothesis," he said.

Bloomberg said the utility's latest estimate was that most of the problems could be fixed by the end of the weekend.

Con Edison also said Friday that 35,000 customers in Westchester County, the suburbs just north of New York City, also lost power after Tuesday's storm. About 6,000 were still out Friday morning.

Bloomberg demanded that the utility investigate and deliver a report on the cause of the outages in Queens within two weeks.

That was little consolation for Gianni DellaPolla, 26, a baker at Gian & Piero Bakery.

"We probably lost $25,000 in business in three days," DellaPolla told the Daily News. "Everything like wedding cakes, eggs, creams, we had to throw all that out."