Mayor de Blasio admitted for the first time Wednesday he was interviewed by investigators probing his campaign fund-raising — but he refused to offer even basic details about his sit-down with the Manhattan DA’s office.

“I’m not going to characterize it — it was fine,” he told reporters at an unrelated press conference in Brooklyn. “I’m not going to get into any details — lawyers can fill in for you. I just told you the factual answer to your question.”

He would only say he met with prosecutors a few weeks ago at the behest of the DA’s office.

“The Manhattan DA’s office asked for an interview and we did an interview,” de Blasio confessed.

Sources told The New York Times that de Blasio was questioned by prosecutors for 90 minutes Dec. 23, and the meeting focused on his fund-raising for state Senate elections.

During the interview, Hizzoner was shown documents related to his fund-raising activities, the paper reported.

De Blasio’s fund-raising is under investigation by both state and federal authorities.

Separate probes are examining if de Blasio and his allies violated state campaign-finance laws in a failed bid to put a Democratic majority in the state Senate in 2014, and if special favors were given to donors to the mayor’s now-shuttered nonprofit, the Campaign for One New York.

Federal and state grand juries have been convened to hear testimony in the cases involving City Hall, but de Blasio said Wednesday that he hasn’t testified before either one.

DA Cyrus Vance Jr. has been probing whether the mayor’s aides urged unions and wealthy supporters to fork over money to Ulster and Putnam County Democratic state Senate campaign committees.

Those committees then allegedly funneled the money to specific Democratic candidates in tight races in an apparent bid to avoid campaign-donation limits.

Top de Blasio aide Emma Wolfe and his campaign fund-raiser, Ross Offinger, who’s now working as a consultant on the mayor’s 2017 re-election campaign, are also targets of the DA’s probe, according to public reports.

US Attorney Preet Bharara is separately investigating CONY, for which the mayor raised $4.3 million to promote his pet projects.

Many of those donations came from individuals and firms with business interests before the city.

Hizzoner has repeatedly maintained that his office has followed the law and that no donors received special treatment.

The city’s Law Department referred The Post’s questions about de Blasio’s sit down with prosecutors to mayoral spokesman Eric Phillips, who would only say the mayor was questioned in “late December.”

As for what was said during the interview, Phillips characterized it as a “voluntary discussion.”

A spokesperson for Vance declined to comment.

Additional reporting by Rebecca Rosenberg