Contract staff at York University in Toronto officially went on strike Monday, two days after rejecting what the university called its “best” offer.

Faculty members, teaching assistants, graduate assistants, research assistants, part-time librarians and archivists went on strike at one past midnight.

The bargaining team for CUPE 3903 said the university’s latest offer did not do enough to protect the job security of contract faculty.

The university has said it will remain open during the strike and says classes will not be impacted.

The union says picket lines will be set up around the campus at 7:30 a.m. Tuesday.

The school’s libraries, restaurants, administrative offices and other services will also remain open.