In a video posted to Twitter this afternoon, Sgt.  Kerry Schmidt of the OPP said the note is about four feet by four feet.
He said the motorcycle operator collided with this object.
The victim was rushed to the Trauma Center and his exact condition is not known.

	Motorcycle rider remains in trauma center and treated, #Hwy401/Meadowvale eb express lanes remain closed for ongoing investigation.  The briefcase fell from another vehicle that the rider collided with.  If you’ve been hauling cargo make sure your equipment is insured #RoadSafety.  pic.twitter.com/W7Vghv9GQs
— OPP Safety Division (@OPP_HSD) August 16, 2022
Currently, the eastbound express lanes of Highway 401 between Meadowvale and Brock roads are closed as police investigate.

	A motorcycle rider hit a container that fell from a vehicle.  Rider with serious injuries.  #TorontoOPP is investigating.  Another vehicle was also located.  #Hwy401/Meadowvale eastbound express lanes closed for investigation.  pic.twitter.com/6Rh2dEMWb3
— OPP Safety Division (@OPP_HSD) August 16, 2022
Schmidt said motorists should expect “heavy” delays.
“It’s going to be a slow ride through this area,” he said.
Police are reminding truck drivers to “make sure your equipment is secure.”