Montreal Mayor Michael Applebaum says he is not the target of a late day raid by Quebec's anti-corruption squad and says he is co-operating fully with investigators, who combed through several municipal offices late into the evening.

Applebaum emerged from Montreal City Hall onto the snowy street at about 9:20 p.m. Tuesday, briefly answering questions from a throng of waiting reporters.

"My objective is to work with the police, to respond to all their questions, and to open city hall so they can find all the information they're looking for concerning the files they're investigating," Applebaum said.

"I am not under investigation — that's clear," he stressed. "I want to reassure Montreal citizens that we are here to co-operate with the police. From the time of my election, I've made it clear I want to shed light on corruption and collusion."

Investigators with Quebec's anti-corruption unit raid Montreal City Hall. (Radio-Canada)

In all, 120 officers were involved in the searches, which began at around 4 p.m. at Montreal City Hall, where all elected officials were told to leave the building.

The offices of Union Montréal, the party of former mayor Gerald Tremblay, were also targeted by investigators.

A spokeswoman from the anti-corruption unit [UPAC] said the raids are connected to an investigation that was opened in 2010 looking into allegations of fraud, the creation of false documents and breach of trust.

Politicians, staff told, 'take only your coats'

Louise Harel, the leader of the Vision Montréal party, was inside city hall when investigators arrived and said an announcement was made telling everyone to leave the building. She said it wasn't clear at the time what was happening

"We'll certainly learn more in the hours to come," she said. "It's exceptional – the City of Montreal the subject of raids. I've certainly never seen it."

Projet Montréal's Richard Bergeron said he had a meeting with the mayor at 4:15 p.m. to discuss the "cultural mosaic."

"When I arrived at his office, it was clear what was important at Montreal City Hall right now wasn't the cultural mosaic," he said.

"There are a lot of UPAC members inside city hall. We got an order to leave the building and we left."

He said those inside city hall were told to take only their coats with them as the building was evacuated.

UPAC said investigators are questioning about 25 people and no arrests are expected.

Six other borough offices are also being searched. They include:

Côte-des-Neiges—Notre-Dame-de-Grâce.

Ville St-Laurent.

Lachine.

Verdun.

Anjou.

Saint-Léonard.

Radio-Canada's senior investigative reporter, Alain Gravel, said aside from Montreal Mayor Michael Applebaum, the former mayor, Gérald Tremblay, as well as former members of the city's executive committee were also questioned.