The Justice Department is investigating donations made by employees of a Little Rock, Ark., law firm to John Edwards' presidential campaign, according to law enforcement sources.

An employee of the firm, law clerk Michelle D. Abu-Halmeh, told The Washington Post last week that her boss, prominent trial attorney C. Tab Turner, asked people to support Edwards and assured them they would be reimbursed.

Campaign donors are not allowed to funnel donations through someone else under federal law. Otherwise, donors could exceed the legal contribution limit for individuals, recently raised to $2,000 from $1,000 per election.

Law enforcement sources told The Associated Press that they opened the investigation after seeing media reports of the donations. They stressed that they are investigating the contributions, not any wrongdoing by the Edwards campaign.

After the reporters uncovered the situation, the Edwards campaign returned $10,000 in donations from five employees of the firm, Turner & Associates.

"We're glad that the appropriate authorities are following up on this mess," Edwards spokeswoman Jennifer Palmieri said Thursday.

Turner's office referred calls to St. Louis attorney Edward Dowd, who did not immediately respond to a request for comment. The Justice Department refused to comment on the investigation.

The North Carolina senator raised $7.4 million in the first quarter, the most of the nine Democrats running for the presidential nomination.

The Edwards campaign gives donors instructions when they contribute, explaining they cannot be reimbursed and other federal guidelines for donations. Last week, the campaign said it would begin sending a follow-up letter after donations are received to remind donors of the law a second time.

Turner earned national prominence by pursing lawsuits against Bridgestone/Firestone Inc. and the Ford Motor Co. for rollover accidents involving failed Firestone tires on the Explorer SUV.