Record-keeping surrounding the Nov. 2 presidential election in Milwaukee is so flawed that in 17 wards there were at least 100 more votes recorded than people listed by the city as voting there.

In two wards, one on the south side and one on the north side, the gap is more than 500, with fewer than half the votes cast in each ward accounted for in the city's computer system, a Journal Sentinel review has found.

Such gaps were present at different levels in nearly all of the city wards and could hamper the investigation launched last week by federal and local authorities into possible voter fraud by giving an incomplete or inaccurate picture of who actually voted.

They also raise questions about the level of oversight of how the city records who voted in each ward - an important safeguard that, properly done, can be used to spot double voting and other problems.

And unless the gaps can be fully resolved, they leave room for critics to allege that ballot boxes were stuffed in the city, which went heavily to Democrat John Kerry over President Bush in a state with one of the closest margins in the country.

[Mayor] Barrett reiterated Tuesday that he welcomes the investigation, which is being overseen by Milwaukee County District Attorney E. Michael McCann and U.S. Attorney Steve Biskupic.

"I don't think we have seen any evidence of fraud," Barrett said. But he acknowledged that vote gaps and other problems shake the confidence of residents and others in the system.

The investigation was launched a day after the Journal Sentinel reported at least 1,200 votes in the Nov. 2 election were cast from invalid addresses. Some are due to transposed digits in addresses, but many others could not easily be explained or the voters readily identified.

Nevertheless, while the Journal Sentinel has found 1,200 votes recorded from invalid addresses and a gap of more than 7,000 unaccounted for votes, there are no guarantees law enforcement officials will be able to identify fraud or charge anyone with it if they do.

Indeed, the same open system that makes it easy to vote on election day, long a point of pride for the state, makes it difficult to determine later if someone voted twice, voted as someone else or intentionally used a bad address.

In other words, it is one thing to find a crime, another to identify who is responsible for it.

What's more, when a crush of voters met an already stressed election system in Milwaukee, it resulted in records that are incomplete, duplicates or - in the case of more than 7,000 votes - not yet accounted for.

State lawmakers who want to require photo identification of voters said Friday that news of voting problems in Milwaukee has given their bill a burst of momentum.

The mounting evidence this week of irregularities in Milwaukee has caused concern around Wisconsin that will result in new pressure for reform, said Rep. Jeff Stone (R-Greendale), one of the authors of the photo ID bill, which is to be introduced Monday.

State residents may worry about their votes being, in effect, negated because of questions surrounding thousands of votes in Milwaukee, he said.

"People in Rhinelander or Rice Lake probably really didn't see election reform as a major issue two years ago, but I think they're beginning to see what goes on around the state, and having integrity in that system is important to every vote cast," Stone said.

The votes came from addresses that were among 5,619 the state Republican Party challenged less than a week before the election as non-existent. The city Election Commission rejected the claim, saying the party hadn't met the high legal standard for removing names from poll lists.

That led GOP officials to question Tuesday whether the city complied with its later agreement to have poll workers seek identification from anyone who attempted to vote from those addresses.

"I don't think there should have been anyone voting from the 5,600 addresses," state GOP chairman Rick Graber said. "We had an understanding. We had an agreement. For whatever reason, the city did not live up to its end of the bargain."