The Toronto Stock Exchange and Montreal Exchange shut down early on Friday as a result of technical problems that began at about 2 p.m. Eastern.
TMX Group, the Toronto-based company that operates the exchanges, announced the unusual decision through Twitter.
A spokeswoman for the company said it is investigating the cause of the disruption. The first tweet was sent out about 2 p.m., with two hours remaining in the normal trading day.
TMX later announced in a statement that it was closing the exchanges for the day.
"TMX has decided to shut down all markets for the remainder of the day, Trading will not resume today, including market on close. We apologize for the inconvenience," the company said.