SAN FRANCISCO (AP) — Prosecutors won't file criminal charges in the case of a property management firm accused of laundering thousands of dollars in contributions to San Francisco Mayor Ed Lee's election campaign last year.

The San Francisco Chronicle reports that prosecutors said there was insufficient evidence to support charges.

The case had centered around $4,500 in contributions to Lee's campaign from employees and associates of Archway Property Services. Lee's campaign returned the money after the newspaper asked about the donations and campaign officials notified prosecutors.

The newspaper said it had an email from Archway's managing director who told workers to write a check at a fundraiser for Lee and promised repayment.

"''I expect each and every one of you to be at this event tonight," Andrew Hawkins-Cohen wrote in capital letters, according to the newspaper. "Bring your check books and write a check for $500.00 for Ed Lee donation. You will be reimbursed right away for you coming."

Eight Archway employees and one worker's spouse donated the maximum $500 to Lee's campaign, records show. State law prohibits reimbursements for a campaign contribution.

Hawkins told the Chronicle last fall that the allegations were "more of an internal misunderstanding" but would not provide details. The company did not immediately respond to an email sent by The Associated Press seeking comment.

Prosecutors also announced Thursday that they would not file criminal charges in connection to voter fraud allegations during the 2011 mayoral campaign. Lee's staffers were accused by rival campaigns of illegally filling out and submitting absentee ballots for elderly voters in Chinatown.

San Francisco District Attorney George Gascon wrote in a statement that he remains concerned by the allegations even though there wasn't enough evidence to file charges.