Market officials and Wall Street's big banks reported few, if any, glitches in their trading rooms after the outage hit. Along with the New York Stock Exchange and the Nasdaq, most trading firms quickly switched over to battery-generated power.

Since the electricity was knocked out shortly after the 4 p.m. close of the markets, the blackout apparently didn't affect investors.

"No data from today's trading has been lost," the NYSE said in a statement. "In addition, SIAC (the exchange's data-processing arm) is operating at normal capacity on generator power. The NYSE is prepared to open on generator power."

Ray Pellechia, a spokesman for the exchange, said it was too soon to tell whether there was any damage sustained from the sudden power loss.

Nasdaq said its computer facility was operating on backup power. After-hours trading continued on the Island ECN and Archipelago networks

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