The RCMP has started interviewing senators in its investigation of the expense scandal, CTV News has learned.

Mounties are treating Sen. Mike Duffy’s improper expense claims as an alleged breach of trust, and obtained campaign records for 12 Conservative candidates as part of the investigation.

They have also widened their probe into the expense scandal to include Senators Mac Harb and Patrick Brazeau, court documents show.

Duffy would not say Friday whether he had been interviewed by the RCMP.

“It would be inappropriate for me to make any comment while these matters are under investigation,” he told CTV News.

Sen. Carolyn Stewart Olson, a member of the committee looking into Senate expenses, and Conservative Senate House Leader Marjory LeBreton say they haven’t yet been interviewed by the Mounties, but expect they will be.

“Obviously if they’re looking into a matter in the Senate and I’m the government leader in the Senate, they will obviously want to ask me if I’ve had anything that I can add to this story,” LeBreton said. “So I’ll be very happy to meet with them.”