BELLEVILLE, Ont. -- Crews are cleaning up an estimated 40,000 litres of lubricating oil that spilled in a massive crash involving roughly 50 vehicles on Highway 401 near Trenton, Ont.

The Ontario Ministry of the Environment says the oil is "non-hazardous" and has been contained to the highway ditch.

A spokeswoman says there are "no concerns for impacts to nearby surface or groundwater."

The collisions, which included several tractor-trailers, happened just after midnight during poor driving conditions.

The eastbound lanes of the highway remained closed in the area by midday but one westbound lane was opened to traffic at about 5 a.m.

Four people reportedly suffered non life-threatening injuries.

More than 50 people were bused to a Ramada Inn in Trenton to spend the night.