A 2nd collision on Highway 401 on Thursday morning has once again shut down eastbound lanes. (CBC)

All eastbound lanes of Highway 401 at Trafalgar Road have been reopened following a collision between two transport trucks on Thursday morning.

Ontario Provincial Police Sgt. Kerry Schmidt said that one of the drivers of the truck suffered "serious or critical" injuries and was transported from the scene by Ontario's air ambulance service.

UPDATE ROAD CLOSURE: <a href="https://twitter.com/hashtag/Hwy401?src=hash&ref_src=twsrc%5Etfw">#Hwy401</a> EB at Trafalgar Rd <a href="https://twitter.com/hashtag/Halton?src=hash&ref_src=twsrc%5Etfw">#Halton</a> <a href="https://twitter.com/hashtag/Milton?src=hash&ref_src=twsrc%5Etfw">#Milton</a> - WB lanes reopened, all EB lanes remain CLOSED. Reopening time unknown. ^lm
—@OPP_GTATraffic

Westbound lanes were also closed for a time to allow the air ambulance to land and take off, but have since been reopened.

Schmidt said he believes the collision may have been caused by the "slowdown" that resulted from an earlier multi-vehicle collision on Highway 401 that happened just a few kilometres away, at Winston Churchill Boulevard.

Earlier collision at Winston Churchill Boulevard

Three people were taken to hospital with minor injuries as a result of that earlier crash, which involved five vehicles in all, including three transport trucks.

The morning's first collision left "a significant amount of damage and debris" at the scene, according to Sgt. Kerry Schmidt. (Kerry Schmidt/Periscope)

Police had re-opened one eastbound lane of Highway 401 and were cleaning up debris from the highway when the second collision happened.

One person was trapped in a vehicle after the first collision, and has since been taken to hospital. (Kerry Schmidt/Periscope)

Highway 401 eastbound lanes reopen at Trafalgar Road after trucks collide

One driver suffered critical injuries, says OPP

Earlier collision at Winston Churchill Boulevard