Major stock exchanges are testing their systems in preparation to reopen Wednesday after Hurricane Sandy forced trading to halt on Wall Street.
The New York Stock Exchange and the Nasdaq were allowing brokerage firms to run tests on their platforms early Tuesday.
If the NYSE's physical trading floor doesn't reopen Wednesday, the exchange's all-electronic platform, Arca, would operate if markets open.
NYSE Euronext, the exchange's operator, denied reports that flooding in Lower Manhattan had inundated its trading floor with three feet of water.
"We stress that, as of now, there has been no damage to the NYSE Euronext NYC headquarters that would impair trading-floor operations," NYSE Euronext said in an alert to traders late Monday.