The irregularities include machines failing to record votes or recording them inaccurately, as well as problems with the way officials counted provisional ballots, which were provided to voters whose names didn't appear on voting lists but who contended they were eligible to participate in the election.

Congress' investigative agency cautioned, however, that it isn't authorized to take action if irregularities are found.

GAO spokeswoman Susan Becker said the investigation isn't a direct response to a recent request by several Democratic members of the House, who asked the GAO to investigate. The GAO was already planning to look at systemic issues related to the elections process after the Nov. 2. election. But given the concern expressed by more than a dozen members of Congress and many voters, the GAO will look at some of the specific problems reported. These include complaints by some voters who said they used touch-screen voting machines that recorded votes for candidates they didn't pick.

The GAO also will examine distribution and allocation of voting machines, since there have been reports in Ohio that some precincts didn't have enough machines to handle the number of people who turned out to vote.

"We are pleased that the GAO has reviewed the concerns expressed in our letters and has found them of sufficient merit to warrant further investigation," said Rep. Jerrold Nadler (D-New York) on his website. "We are hopeful that GAO's nonpartisan and expert analysis will get to the bottom of the flaws uncovered in the 2004 election."

To aid the GAO's inquiry, the legislators will provide copies of specific incident reports their offices received, including more than 57,000 complaints that they already have provided to the House Judiciary Committee.

"We are literally receiving additional reports every minute," lawmakers said in their letter to the GAO. "The essence of democracy is the confidence of the electorate in the accuracy of voting methods and the fairness of voting procedures."

GAO's Becker said the agency doesn't have a date yet by which it will complete its investigation, but it is highly unlikely that a report will be completed before members of the Electoral College meet Dec. 13 to cast their presidential votes.

The GAO investigation is not being conducted with any expectation of altering the election outcome. Most counties across the country have already certified their election results, and a deadline for requesting a recount in Florida passed Tuesday. Two candidates, from the Green and Libertarian parties, have requested a recount in Ohio, but a judge ruled this week that the recount cannot begin until after the state certifies its results Dec. 6. Bush beat Democratic challenger John Kerry by 136,000 votes in Ohio, according to the state's unofficial count. A partial recount of some New Hampshire precincts has so far shown a difference of only about 15 votes from the original count.

Will Doherty, executive director of the Verified Voting Foundation, said his group was very pleased with the GAO's decision to investigate the election, in light of the more than 900 reports his organization received on election night.

"We received reports about problems with e-voting machines that spanned across all voting machine vendors and many locations around the United States," Doherty said. "If the GAO is able to confirm that there were incredible variety of problems with virtually every type of e-voting machine, then that lays the groundwork for dialogue with election officials to change election processes, improve voting technology and update election regulations."