New York Mayor Bill de Blasio will not face charges after a year-long fundraising probe, officials said on Thursday.

The Manhattan District Attorney’s Office said that despite the Board of Election’s view that the mayor’s conduct “may have violated the Election Law, this office has determined that the parties involved cannot be appropriately prosecuted.”

Investigators have been poring through finance records from the mayor’s 2013 campaign, amid questions about how campaign officials solicited donations from the city’s real estate and business sectors.

The U.S. attorney and his staff also were looking into whether individuals may have benefited from those donations.

The mayor had insisted donors are not entitled to favoritism. “If someone makes a donation, that’s their choice, they should expect nothing in return,” de Blasio said during the investigation.

On Thursday, Acting U.S. Attorney Joon Kim confirmed that the office would not bring charges against the mayor.

“We do not intend to bring federal criminal charges against the Mayor or those acting on his behalf relating to the fundraising efforts in question. Although it is rare that we issue a public statement about the status of an investigation, we believe it appropriate in this case at this time, in order not to unduly influence the upcoming campaign and Mayoral election,” said a statement issued by the office.”