Service is on hold across the Toronto and Hamilton area's commuter rail system due to a power outage at the CN Rail traffic control centre.
GO Transit says the outage has caused signal failure throughout the system and all trains on the Lakeshore West line will stay where they are until signals are back up.
It says riders can use their fares to switch to the Toronto Transit Commission system.
GO Transit says it runs 252 weekday train trips carrying an average of 215,000 passengers.
It also operates a network of commuter buses, which are unaffected by the current power outage.
VIA Rail service also appears to have been halted by the same outage.
with a file from Siobhan Morris