At least 39 vehicles collided on Highway 400 in Barrie, Ont., bringing the southbound lanes to a standstill on Wednesday, Ontario Provincial Police say.

The massive pileup appears to have been caused by snowy weather in the area, Sgt. Kerry Schmidt said.

No one was seriously hurt, though four people were taken to hospital with minor injuries.

Emergency crews were called to the scene near Bayfield Street mid-afternoon.

"It has been just a really overwhelming day for many first responders in that area," Schmidt said.

Police said earlier that up to 50 vehicles were involved, but Schmidt later said investigating officers had counted nearly 40. A transport truck was also involved.

No charges have been laid, but police are continuing to investigate, Schmidt said.

Danielle Strohm lives near the scene of the pile-up and passed the wreckage on her way home.

Sgt. Kerry Schmidt says there are no serious injuries. (Stefan Ottenbrite/Twitter) Strohm said the road felt like "sheer ice," even though she still using snow tires — "we don't take them off until May, you learn that up here," she said.

By the time she reached the area, amid nearly whiteout conditions, traffic was moving at a crawl. Strohm said at least one fire truck raced past her on the way to help the motorists involved in the crash.

Strohm said she couldn't count how many vehicles were involved, but was relieved to hear everyone is OK.

Even getting off the highway was difficult, she added.

"It was so slippery I had trouble moving."

The southbound lanes of Highway 400 had been closed but reopened around 6 p.m.