A collision between a TTC bus and a tractor-trailer sent 18 people to hospital and slowed traffic in Toronto's west end Wednesday morning.

More than a dozen passengers were taken to hospital after the bus crashed into the rear of a tractor-trailer in the southbound lanes of Highway 427 near Bloor Street at about 7:30 a.m.

One person was taken to hospital with serious injuries while the rest suffered superficial injuries and neck pain, according to Toronto EMS.

There were about 33 people on board the bus at the time of the crash. Those not taken to hospital were picked up by a second bus and taken to their destination.

Two southbound lanes of Hwy. 427 were closed following the collision but reopened to traffic shortly before 10 a.m.

Police continue to investigate the cause of the crash.