A statement on the university website, which is attributed to York president Mamdouh Shoukri, indicates that a labour disruption is in effect as of Tuesday.
"The strike is unfortunate. It impacts the entire York community, particularly our students. I know that students and their parents are very concerned — I share their concerns," Shoukri says in the statement.
Shoukri says the labour disruption involves CUPE Local 3903, which represents nearly 3,700 teaching assistants, contract faculty, graduate assistants and research assistants.
"To provide clarity to our students for the duration of the strike, we have regrettably suspended classes, with limited exceptions," Shoukri says.
"However, all York facilities, including libraries, residences, computer labs, cafeterias, athletic facilities and offices will remain open during their usual operating hours."
York is advising its students to check its website for updates.
The CUPE Local 3903 website did not immediately have a statement posted as of late Monday night, but its Twitter feed indicated that its members would be on strike as of 12:01 a.m. Tuesday.
Faiz Ahmed, the chair of CUPE Local 3903, told CBC News that members had voted 71 per cent to reject an offer that had been made by the university.
But he said the union is sending its bargaining team back to the table on Tuesday.
"We believe we're not that far apart and we think we can come to an agreement sooner (rather) than later," he said.