A three-car crash on the 403 by Waterdown Road has sent one person to hospital and forced traffic to a crawl in the area.

The OPP first tweeted about the accident at 7:40 a.m. One person has been taken to hospital with serious but not life-threatening injuries, said Sgt. Kerry Schmidt. All of the eastbound lanes of the 403 are closed with traffic exiting at Waterdown Road.

“The westbound lanes are also jammed,” Schmidt said.

Schmidt says the accident happened when a 51-year-old Oakville woman driving in the westbound lanes was hit from behind by another car, pushing her into a tractor-trailer. She then lost control, crossed over the median, and hit another car in the eastbound lane.

"The two vehicles in the eastbound lanes have significant damage," Schmidt said. "One is on its side, and one has front end damage."

Police estimate it would probably be two to three hours before the lanes reopen. It's too early to say if charges will be laid or if alcohol was a factor, Schmidt said.

The York Boulevard ramp to the eastbound 403 is closed.