Members of the union representing GO Transit bus operators, station attendants and other employees are on strike.
The Amalgamated Transit Union Local 1587 issued a statement Sunday evening saying it was unable to secure a new contract with Metrolinx.
The strike began at 12:01 a.m. Monday and Metrolinx says bus service is suspended in light of the walkout, though train service remains and stations are open.
ATU Local 1587 president Rob Cormier said Sunday bargaining talks broke down over safety concerns related to hiring contract workers from outside companies.
Metrolinx issued a statement saying the union walked away from weekend negotiations and declined a request to return to the table on Monday.
The union, which represents about 2,200 GO Transit workers, has said key issues include job security and job safety relating to hiring contract workers from outside companies.
