Officials from the city and province are investigating an oil spill into the Humber River in northwest Toronto this week and say efforts to clean up the spill by the company responsible are expected to begin on Thursday. Toronto Water, the Ontario Ministry of Environment, Conservation and Parks and its Spill Action Centre are investigating the spill into the river southwest of Finch Avenue West and Weston Road. There's no word yet on the amount that was spilled, but the ministry said it is machine oil.