Two airliners collided on the ground at Toronto's Pearson International Airport on Friday night, causing a small fire on one and an emergency evacuation of the other.

WestJet Flight 2425, arriving from Cancun, had 168 passengers and six crew on board, and was waiting to proceed to the gate when a Sunwing aircraft backed into it, around 6:20 p.m. ET.

The Sunwing aircraft was not carrying any passengers or crew, according to Beverly MacDonald, a representative for the Greater Toronto Airport Authority. It was being towed by the airline's ground crew.

MacDonald said an investigation is underway.

While there were no injuries on the WestJet flight, one member of the Toronto Pearson Fire and Emergency Service was injured and has been taken to hospital.

Fire and emergency services responded and the WestJet passengers exited via two emergency slides.

The airport says operations have "largely not been affected" by the accident, but "continue to be challenged by the extreme cold weather conditions." The temperature in Toronto is expected to dip below – 20 C overnight.

'It was chaos'

When the planes struck, amusement turned to panic on board WestJet's Boeing 737-800, according to passenger Gustavo Lobo.

"Out of nowhere there was an audible crunch and the plane rocked slightly," Lobo told CBC News. "We looked out the window and saw that the plane had backed up into us. Everyone was a little shocked and kind of chuckling at the situation."

They didn't laugh for long, he said.

"Panic set in when [we saw] what seemed to be fuel spewing from the crash. After a couple of seconds the entire thing ignited and it was chaos inside the plane. People screaming and panicking all while the flight attendants shouted to try and control the situation."

Lobo took a video of the fire, and said eventually everybody slid down the emergency slides to safety, though the process was slowed by passengers who insisted on taking their carry-on luggage with them.

Fire and smoke

Ali Alagheband, also on the flight with his wife and 12-year-old son, said a "big ball of fire" lit up the right-side windows just seconds after the plane rattled with the force of the collision.

"Everybody was saying the F-word and screaming," Alagheband said, adding that he mostly stayed calm until black smoke seeped into cabin.

"The flight attendants kept saying 'remain seated, remain seated,'" he recalled. Fearing they'd soon be gasping for air and stuck on the plane, he told his son to stay calm and wear an oxygen mask if they fell from the cabin's ceiling.

"There was fire and there was fuel in that wing," he said. A mechanical engineer by trade, he could tell "it wasn't a good situation."

Nobody knew an evacuation was underway until a passenger stood on his seat and yelled that a door had opened, he said.

But as the crowd moved toward the door, some passengers blocked his family's escape.

"I was yelling at people reaching overhead to get their bags. It was ridiculous," he said. "I was literally yelling, 'Get the F off the plane."

'Nobody knew what was going on'

John-Ross Parks, 32, was aboard another plane, to Fort Lauderdale, beside the Sunwing aircraft. They were waiting to depart when passengers around him began to complain of a funny smell. Parks figured it was just exhaust.

But half an hour after their scheduled take-off time, Parks said, people noticed something amiss.

"The air was full of fumes," he told CBC Toronto. As the plane grew more restless, somebody looked out the window, he said, and saw the burning Sunwing flight next to them.

Update: As of 21:00, all Westjet passengers have been safely returned to the terminal and are being cleared through Canadian customs. More info available here: <a href="https://t.co/b9cBJMg7uF">https://t.co/b9cBJMg7uF</a>. <a href="https://t.co/5hnMRb9TIF">https://t.co/5hnMRb9TIF</a> —@TorontoPearson

Parks, who was en route to catch a Caribbean cruise with his mother and grandmother, said his flight was cancelled in the pandemonium.

"I've never seen so many emergency trucks," he said. "Nobody knew what was going on."