One person is dead after a semi tractor-trailer travelled the wrong way on Yellowhead Drive, plunged off an overpass and fell onto the train tracks below.

Fire crews have been called to the scene, located east of 184 Street near 118 Avenue, to battle the flames coming from the vehicle.

Stony Plain RCMP Const. Barb Roy said they received five reports from drivers saying they had to go into the ditch to avoid the truck that was driving the wrong way on the Yellowhead.

"The reports said he was very erratic going from lane to lane," she said.

The truck was reportedly travelling eastbound in the westbound lane around 170 Street around when it hit the median, spun out of control and plunged off the overpass.

Police said early information shows the driver began behaving erratically about 25 kilometres west of Edmonton -- a trip that lasted about 20 minutes and left many cars in the ditch.

William Acevedo said he was driving on the highway on his way to work with his daughter in his car around 1:15 p.m. when he saw the truck barrelling towards them.

"I could see the driver, he looked zoned out. We came that close to a head-on collision," he said.

"He looked angry, mad. He looked zoned out."

Acevedo ran his car into a nearby ditch. He said he feels lucky to be alive.

"Something told me to go to the left and that's why we're here today," he said.

Police spokeswoman Karen Carlson said the driver died on scene.

Other witnesses said the truck was travelling very fast before spinning out of control.

"I saw all the trucks bailing into the ditch in the centre of the road and the truck in front of me went across and I was staring at the bush bumper of a semi truck coming at me," Cameron Sharp said. "He was probably doing 100 (km/hr)."

"He veered off and hit the end of the abutment there," John Phillips said. "Five seconds later his tank let go and there was a huge fireball after the truck went down."

Early reports from the scene indicate the truck was carrying large cardboard trays used for transporting bread and bottles of pop.

Debris from the impact landed on the CN tracks, affecting train traffic in the area, Carlson said.

No other serious injuries are being reported.

Both lanes on the Yellowhead were shut down this afternoon. Eastbound traffic is now reopen and westbound traffic is being rerouted at 178th Street.