WestJet announced shortly before 9 p.m. CT Monday that Flight 442 had been diverted.
The airline then tweeted at 9:14 p.m. that the flight had landed at Winnipeg James Armstrong Richardson International Airport and passengers and crew had disembarked.
CBC videographer Lyzaville Sale, who is at the scene, reports seeing a number of fire trucks, ambulances and police vehicles on the tarmac.
Richard Bartrem, WestJet's vice-president of communications, issued the following statement shortly after 9:30 p.m.:
"Following standard procedure in response to a threat, #WS442, Edmonton to Toronto, has diverted and landed at Winnipeg International Airport. Guests and crew have evacuated the aircraft. Emergency responders are working with our crew to secure the site and ensure the safety of our guests and crew."
Neither WestJet nor the Winnipeg Airports Authority has specified what the threat was.