D.C. Mayor Muriel E. Bowser’s campaign committee has been fined for taking campaign donations in excess of legal limits. (Jabin Botsford/The Washington Post)

D.C. Mayor Muriel E. Bowser’s campaign committee has been ordered to pay $13,000 in fines for taking campaign donations in excess of legal limits during her successful run for office three years ago.

Bowser’s campaign kept over $11,000 in illegal contributions from 13 developers, contractors and Sanford Capital, a landlord that her administration has since been slow to fine for more than 1,000 housing-code violations.

The illegal contributions were first discovered in March by the nonprofit organization Public Citizen, which aims to limit the influence of money in politics. The D.C. Office of Campaign Finance had not said if it would investigate the allegations. However, late Tuesday it released documents saying several of the violations had been substantiated and that Bowser’s team had already returned the excess money.

The fines come at an inopportune time for Bowser, highlighting her close ties to some of the city’s largest developers and property managers as she has begun gearing up for a reelection fight in which displacement from gentrification will probably be a major theme in economically disadvantaged neighborhoods across the city.

Some of the developers who contributed more than the legal limit to Bowser in 2014 were the same ones who went on to contribute to a political action committee that Bowser’s allies set up but later abandoned during her first year in office amid criticism from council members that it was creating a perception of pay-to-play politics.

Public Citizen seized on the fines assessed to Bowser, who ran on a pledge of cleaning up city government, to press for campaign finance reform.

D.C. Attorney General Karl A. Racine, a possible challenger to Bowser, has introduced a bill that would preclude any company that makes a campaign donation from seeking a contract with the District government for at least a year afterward. Bowser has been lukewarm to the proposal.

The council’s judiciary committee is scheduled to begin debating that and other campaign-finance reforms in July — probably too late to affect how campaigns raise or report money in next year’s mayoral election.

Bill Lightfoot, Bowser’s former campaign chairman, called the excess campaign contributions mistakes and said the mayor was accepting responsibility and would not appeal the fines. “We admit it,” Lightfoot said, “and we’re moving on.”

But Public Citizen called on the mayor to apologize to voters personally and said the violations raise questions about her fundraising apparatus, led by the mayor’s longtime campaign treasurer, Ben Soto.

The fines marked the second time in as many months that Soto was in charge of a campaign fined by the Office of Campaign Finance. Soto was also the treasurer for the 2015 special-election campaign to elect Brandon T. Todd, Bowser’s hand-picked successor to take her seat on the D.C. Council.

The District’s election regulator said last month that Todd has been unable to produce canceled checks or other evidence to prove the origin of over $85,000 in campaign contributions deposited in his account. It fined Todd $5,100, a fraction of what watchdog groups said was appropriate.

The Office of Campaign Finance also charged Bowser half of the fine that it could have under city statutes. The director of the agency cited Bowser’s cooperation and quick work to return excess money for lowering the fines. But at $13,000, Bowser has the unwelcomed distinction of having been fined a larger amount than the $10,000 levied for unreported contributions and expenditures by her predecessor, former mayor Vincent C. Gray, who may also seek a rematch with Bowser.

Bowser “has yet to apologize to the public for taking illegal money — that’s the minimum we should expect,” said Aquene Freechild, a co-director of Public Citizen’s Democracy Is For People campaign. “Our elected officials should be the first to obey the laws they enact and sign.”

Because of the way OCF chose to levy fines against Bowser’s campaign, she has been allowed to fundraise to cover the expense of returning the excess donations, as well as to cover the fine amount. Lightfoot said fundraising is more than halfway done, with about $9,000 in donations still needed for Bowser to cover the fine.