A 34-year-old woman is dead after a fiery, multi-vehicle crash on the Queen Elizabeth Way in Oakville, Ont., provincial police say.

The collision occurred shortly before 11 p.m. ET Thursday a short distance east of the exit for Trafalgar Road, said provincial police Const. Lauren Ball.

The highway was closed to traffic throughout the night and early morning as crews worked to clear "a very large debris field" strewn across the roadway, Ball said. It did not fully reopen until 12:45 p.m. Friday.

Ball said a tractor-trailer hauling a load of fruit and six passenger vehicles were involved in the crash on the QEW, a busy highway used to travel to and from the Greater Toronto Area.

Badly burnt-out vehicles and debris were strewn across the highway. (Jeremy Cohn/CBC)

OPP officers initially believed no one had died in the pile-up, she said. After a tow truck moved the transport truck, however, a car was discovered crushed beneath it.

The 34-year-old, from Niagara Falls, Ont., was found dead inside the car, Ball said. Police haven't released her name.

Seven other people were taken to a local hospital for non-life-threatening injuries.

Sonny Subra, a tow truck operator who was among the first to arrive at the crash site, said the transport truck was engulfed in flames. At least one other car was also on fire, he said.

"This is chaos here," Subra told CBC Toronto. "The cars are mangled."

The OPP's collision reconstruction team was at the site Friday and a coroner was called to the scene.