The search for a nine-year-old boy who fell through ice in Lake Erie has turned into a recovery mission, Ontario Provincial Police say.

"With these cold temperatures and the water, it's now a recovery," Const. Mary Boddy of the Haldimand County OPP told CBC News.

Police say the boy is presumed to have drowned.

Emergency crews were called to Peacock Point, about 60 kilometres south of Hamilton, Ont., around 4:30 p.m. for reports that two little boys had fallen into the water.

Two nine-year-old boys were on the ice near the shoreline along with a 10-year-old girl at the time.

"The little girl that was playing with them ran to get help and was able to flag down a passerby," Boddy said. "The passerby along with the little girl's grandfather were able to rescue one of the boys."

That boy is in hospital in fair condition, said Boddy.

The other nine-year-old did not resurface. Police said the boy is the little girl's brother.

By 9:40 p.m., the effort was deemed a recovery mission. Recovery efforts are expected to continue Sunday morning.

The lake is not frozen, and the ice the children had been playing on broke through because of the mild temperatures, police said.

"We'd like to make it very clear that the place to play is not on the ice, not to go out on your ATVs or snowmobiles and not to go on foot onto the ice, because it is very unpredictable," said Boddy.

"Our hearts, thoughts, sympathies go out to the families of the victim," she added. "It's an unfortunate tragedy."