Prosecutors from the Manhattan district attorney’s office have interviewed Mayor Bill de Blasio in connection with an investigation into his fund-raising practices, the mayor said on Wednesday, his first acknowledgment of direct contact between himself and investigators in a set of overlapping inquiries.

“The Manhattan D.A.’s office asked for an interview and we did an interview,” Mr. de Blasio said in response to a question from a reporter at an unrelated news conference on traffic safety. Asked to clarify who was present, he said, pressing his hand to his chest, “Me, and my lawyers.”

He did not provide the precise date of the interview, saying it had occurred “a few weeks back,” or offer any details of what was discussed, referring questions to his lawyers.

Two people with knowledge of the matter said the interview took place on Dec. 23, lasted 90 minutes and focused on the mayor’s fund-raising in connection with his unsuccessful effort to help Democrats take control of the State Senate in 2014. One of the people said that prosecutors presented the mayor with a variety of documents related to the fund-raising during the questioning.