TORONTO -- Police are investigating a collision involving three motorcycles on Highway 401 at McCowan Rd in east-end Toronto.

Investigators say the three sport bikes were travelling together in the east-bound lanes last night around eight o`clock when -- for reasons unknown -- they collided with each other.

One rider, a 28-year old man, suffered life-threatening injuries.

The other riders, both 45-year old males, were treated for minor injuries.

The OPP and Toronto Police are both investigating and would like to talk to anyone who witnessed the collision.