Tuesday could be a long day for election officials in states relying on electronic-voting machines to record votes in the U.S. presidential election, if early reports of malfunctions are any indication.

Problems with e-voting machines were reported early on election day in several U.S. states, including Florida, Ohio, Pennsylvania and Virginia, which are identified as battleground states where the outcome of the vote could tip the presidential race in favor of either Democratic Sen. Barack Obama or Republican Sen. John McCain.

According to voter reports on the ground and from watchdog organizations, there were problems with getting e-voting machines up and running in these key states and others, and in some cases the machines would crash during the voting process and had to be rebooted.

Pennsylvania and Virginia were among states Verified Voting, an advocacy group focused on improving voting systems, and other watchdog organizations said they would keep a close eye on for voting problems. Neither state had early voting before Nov. 4, nor do they require paper-trail backups with the touchscreen electronic-voting machines in place at polls.

Critics of e-voting say that without a paper trail, there's no way to audit the results of a touchscreen machine, often called DREs, or direct recording electronic machines.

Some polling locations can give voters so-called "emergency" paper ballots, but this is not the case in all locations, said Pamela Smith, executive director of Verified Voting, in an interview early Tuesday. "There is no clear policy on emergency paper ballots, or on when to distribute them so voters can still vote," she said.

Moreover, if there is widespread failure with machines, locations with paper ballots are "concerned they'll run out," Smith said.

This, in fact, happened at one location in northern New Jersey Tuesday morning, where emergency paper ballots were gone by as early as 9:30 a.m. local time. Polling officials began making photocopies of paper ballots because people who came to vote were leaving the site, frustrated by the delay.

By 10 a.m. local time, the Richmond Times-Dispatch newspaper in Virginia reported on its blog of voting news that it received widespread reports of e-voting problems, including trouble with the wireless communication systems of voting machines in Godwin, which the registrar there was quoted as attributing to human error. While that issue was fixed by about 6:45 a.m., other e-voting miscues were cited by the newspaper, as well as reports of a problem with ballots jamming in the feed of a machine that reads marked ballots.