Nevada's position as a battleground state in the upcoming presidential election has sparked an increase in fraudulent voter registrations (search) in southern Nevada, a top election official said.

Larry Lomax, Clark County (search) registrar of voters, said his office has identified several hundred questionable registrations among the 5,000 registration forms submitted to his office every week.

The Nevada Attorney General's Office is investigating.

"We've never seen anything close to this," Lomax said. "There are stupid criminals out there, and there are smart ones. We can spot the stupid ones because they submit them in a stack."

Because of the state's swing-state status, political groups including both state parties are paying people by the hour to register voters, a common practice.

However, some groups are apparently paying for each registration form filed, which is against both state and federal law.

Lomax said some people have told him they were paid by the form. One person mistakenly included his pay stub in a stack of voter registrations that showed him being paid by the form, not by the hour.

"It's useless to do that kind of fraud," said Terrence Tolbert, state director of America Coming Together (search), a national voter registration group. "You can't turn out fake registered people to vote."

A number of nonprofit groups, including Rock the Vote (search) and the New Voters Project (search), are also registering voters in Nevada.

Lomax said as many as 100 different groups have asked his office for voter registration forms. The forms are numbered and recorded to monitor each group's efforts.