Applebaum said he is "working in collaboration" with provincial police but couldn't reveal where the raids were carried out or with whom police spoke, The (Montreal) Gazette reported Tuesday.
However, the major said his home wasn't searched and that the investigation "doesn't touch me."
The permanent anti-corruption unit, known as UPAC, raided Union Montreal offices and seven borough offices about 4 p.m. Tuesday.
The searches began at City Hall, where everyone was told to leave the building and were allowed to take only their coats, the Canadian Broadcasting Corp. reported.
A UPAC spokeswoman said the raids were connected to an investigation that began in 2010 of allegations of fraud, the creation of false documents and breach of trust.
The spokeswoman said about 25 people had been questioned and that no arrests were expected.
Former Mayor Gerald Tremblay and former members of the city's executive committee were reported to be among those questioned.