Toronto’s Pearson International Airport says normal operations have resumed after a fire broke out in Terminal 1 on Sunday night, forcing numerous flight cancellations and delays.

The fire started in the ceiling of a duty free store on the lower level of the terminal sometime before 6:30 p.m.

It was quickly extinguished, but the terminal filled with smoke, prompting an evacuation.

All U.S.-bound flights were cancelled, as well as some international flights.

“Over a period of several hours, approximately 10,000 passengers aboard 50 aircraft were moved from their planes into the terminal,” Toronto Pearson said in a statement.

“At this time, the cause of the fire is currently under investigation and we cannot speculate.”

Early Monday, stranded passengers could be seen sleeping in the terminal, waiting to catch a new flight.

Terminals 1 and 2 were operating normally by early Monday morning, with the exception of departing flights to the United States from Terminal 1. The U.S. departures portion of Terminal 1 returned to normal shortly before 11 a.m.

However, the airport still advised people to check ahead before heading out to catch a flight.

“Some delays are still possible given yesterday’s events,” Toronto Pearson said.

“Airlines are working diligently to re-book passengers who were impacted. We recommend passengers contact their airlines with any questions regarding delayed or cancelled flights.”

Police previously said they found nothing to suggest the fire was suspicious, but indicated that the investigation was ongoing.