Emergency crews in Saskatoon are on scene at the airport after an incident on WestJet flight 391.

Saskatoon police said a threatening call was received, reporting that a bomb was on board the Halifax to Edmonton flight. The flight landed in Saskatoon at about 9 a.m. CST as a precautionary measure.

The plane was diverted to Saskatoon because of the threat. All passengers are off the plane.

Passenger Rob Tomlinson said passengers were told the stop was due to operating issues.

"The first thing that came into my mind was there was probably a threat with luggage or something that didn't pass. I was thinking bomb," he said.

Tomlinson, who's from New Glasglow, Nova Scotia, said he has flown on WestJet hundreds of times and has never encountered a similar situation.

Overall the situation was handled well by the airline, he said.

"The whole atmosphere on the plane was calm. Everybody was pretty good. I think they maybe just made it sound like an operational issue just for the sake fo keeping everybody calm," said the Nova Scotian.

About 150 crew members and passengers had to be taken off this flight from Halifax to Edmonton once it landed in Saskatoon. (Submitted by Dave Zethof)

Wade Wick said no one on board knew anything was wrong. He said he wasn't too worried.

"A little information would have been nice, but I think if they would have told us there was a bomb threat on the plane, while we were on the plane, it would have caused a panic," he said.

Saskatoon Police spokeswoman Kelsie Fraser said about 150 crew members and passengers had to be taken off the plane once it landed.

"It's a criminal investigation at this point," Fraser said.

This passenger is relieved to be off the plane; there were about 150 onboard & lots of kids <a href="https://twitter.com/hashtag/cbcsk?src=hash">#cbcsk</a> <a href="https://twitter.com/hashtag/yxe?src=hash">#yxe</a> <a href="http://t.co/juWUC17aQc">pic.twitter.com/juWUC17aQc</a> —@MadelineKotzer

Police continue to search the plane.

The police service also shared this photo of an officer dealing with pets on the flight: