Gilles Deguire, borough mayor of Montreal North, is under criminal investigation, prompting him to step down Thursday from his position.

The resignation was confirmed by Harout Chitilian, vice-president of the City of Montreal's executive committee.

"We confirm there has been a resignation and it has been confirmed to us, without more detail, that there is a criminal investigation underway concerning the person in question," Chitilian said. "It's a surprise."

Chantal Rossi, a city councillor in Montreal North, told CBC everyone in the community is stunned by the news.

"It's like a bomb. In the borough...even some citizens wrote to me. Everyone is in shock," Rossi said.

"He meant a lot to Montreal North. He's been here since 2009," she said, adding that he was very involved with local organizations.

Rossi said the criminal investigation involving Deguire is not related to his work in office.

"It has nothing, nothing to do with his role as a mayor of Montreal North," she said.

"That's why we won't make any comment regarding this inquiry."

Rossi will replace Deguire as interim mayor until a byelection can be held.

Montreal police are heading the investigation. Deguire has not been charged.

Before entering municipal politics, Deguire worked as a Montreal police officer for 30 years.

He also served 10 years alongside Bourassa-Sauvé MNA Line Beauchamp and served as Union Montreal's vice-president in the east end of the island.

Deguire became mayor of Montreal North in 2009.