(Reuters) - Canadian National Railway Co on Monday said its environmental experts are continuing the clean-up of a site in Western Canada where one of its trains derailed on Saturday.

Thirty-seven tank cars derailed near St-Lazare, Manitoba, close to Assiniboine River, leaking an undetermined volume of crude oil.

None of the crude oil entered the Assiniboine River, and train movements resumed at 12 P.M. local time on Sunday, CN spokesman Jonathan Abecassis said in a statement.

The cause of this incident is under investigation, CN said.