LONDON, Ont. - Police are investigating after a man was dropped off at a London, Ont., hospital with a stab wound Saturday morning.

They say the man underwent emergency surgery, but remains in critical condition.

Police say he was dropped off at the hospital at about 4:30 a.m.

Investigators say they don't know when or where the stabbing occurred, and nobody has been arrested.

Police are asking anyone with information to come forward.