Two people are in critical condition after a chain-reaction collision on the Don Valley Parkway, resulting in a lengthy closure Wednesday afternoon.

Emergency crews were called to the southbound lanes of the DVP near Highway 401 shortly after noon for a collision.

Toronto police said it all started when the driver of a Nissan Sentra, who they said was travelling at a high rate of speed, changed lanes and struck a Chevrolet Silverado that was travelling in the same direction.

The driver of the Chevrolet Silverado then struck a blue dump truck. Meanwhile, the driver of the Nissan Sentra lost control and hit a barrier on the west side of the highway, police said.

The occupants of the Nissan Sentra, who police say are a 42-year-old man and a 20-year-old woman, suffered life-threatening injuries and were transported to hospital.

The drivers of the other vehicles did not have any injuries and remained on scene.

The collision closed the DVP from Highway 401 to York Mills Road for several hours, including for most of the afternoon rush, as police investigated the cause.

The Highway 401 ramp onto the southbound DVP was also off-limits for several hours. During the closure, drivers heading southbound on Highway 404 were redirected to the eastbound or westbound Highway 401.

The DVP reopened just before 5:30 p.m.

Police ask anyone with information to contact Traffic Services at 416-808-1900 or Crime Stoppers anonymously at 416-222-TIPS (8477) or