Rescue crews in southern Ontario are searching for a three-year-old boy who police say was ripped from his mother’s arms after a van was swept into a swollen river.

The incident occurred just before 1 a.m. near the town of Grand Valley, located approximately 100 kilometres northwest of Toronto, Ont.

Ontario Provincial Police Const. Paul Nancekivell said that the mother, who is from the area, drove past a road block that was in place due to flooding and her van was swept into the river.

The mother managed to get her son out of the van but was “pushed over by water, lost her grip on the son and he was swept away in the river,” the constable said.

The mother was taken to hospital and treated for hypothermia, Const. Nancekivell said. The van was later found under a bridge about four kilometres downstream.

Const. Nancekivell said police are using a helicopter with thermal imaging, a drone and an underwater search team to try to locate the boy.

“We hope to find him soon,” Const. Nancekivell said. “It’s a horrible day for us, unfortunately.”

Const. Nancekivell said that although it was a foggy night, the road closure was well-marked. He said an investigation is underway. Police do not believe alcohol was a factor, according to Const. Nancekivell.

Grand Valley Fire Chief Kevin McNeilly told CTV Toronto that a resident called 911 to report headlights bobbing and pointing upwards out of the river.

McNeilly said crews had managed to run a cable from the riverbank to the van to prevent it from floating away.

Brad Patton, the fire chief for Centre Wellington Fire and Rescue that assisted the Grand Valley Fire Department with the rescue, said in a tweet that crews were dealing with “fast moving water” and “large ice flows” in the river.

With files from CTV Toronto and CTV Kitchener