Ontario Provincial Police have closed a stretch of Highway 11 after what's described as a "serious motor vehicle collision."

The approximately 150-kilometre stretch runs from Longlac, Ont. to the intersection with Highway 631, about 60 kilometres west of Hearst, Ont.

The closure began at 1 p.m. ET on Sunday, and was expected to last "quite some time," according to a police news release.

Provincial police in Hearst, Ont. could not be reached to provide more details on the collision. Police in Thunder Bay say they were only called in to assist with the road closure, and could provide no details on the collision itself.