Ontario Provincial Police (OPP) say multiple collisions near Brantford, Ont., — which have seen at least 10 vehicles crash and four transport trucks jackknife — have closed an eastbound lane on Highway 403.
OPP Sgt. Kerry Schmidt told CBC Hamilton "white out conditions" played a role in the crashes.
He said one crash involved seven vehicles and another involved three vehicles.
There are "serious injuries" but it's unclear how many, he said.
Schmidt said on X, formerly Twitter, the eastbound lane is closed between Garden Avenue and Highway 52.
"Expect delays," he wrote.
Images from the scene, shared by OPP, show one transport truck on its side and another jacknifed.
OPP officers from Burlington are at the scene and westbound lanes are still open.
Environment Canada placed Brantford under a snow squall warning earlier Tuesday afternoon.
Brantford is set to see between 10 and 20 centimetres of snow with "intense snowfall rates" and "very poor visibility at times."
Strong winds gusting to 60 kilometers per hour will also make it harder to see.
"Prepare for quickly changing and deteriorating travel conditions. Consider postponing non-essential travel until conditions improve," Environment Canada said.