A video posted on YouTube shows an angry showdown between striking members of CUPE 3903 and people trying to get on campus.
Some drivers were trying to cross the picket line at one of the entrances to York. But when striking teaching assistants forced them to wait, tempers quickly flared. (Warning: The video contains coarse language.)
"Three individuals got out of their cars and become really quite aggressive and they started gesturing," said CUPE 3903 union member Laura Pin.
"They started making threats. They seemed to be looking to pick a fight."
Teaching assistants and other staff walked off the job at York on March 3, though one of the three bargaining units has since returned to work. York has been gradually resuming classes, which are cancelled when the strike first broke out.
TAs and other members of CUPE 3902 are also on strike at the University of Toronto
York said in a statement it is aware of the "deeply concerning" incident.
Police were brought in but no charges were laid. Police say the investigation is now closed.