© unknownA WestJet plane lands on the tarmac in this undated file photo. A WestJet flight headed to Toronto was forced to make an unexpected landing in Thunder Bay, Ont. after a bomb scare.
A Portuguese man on a Toronto-bound Boeing 737 jet whom airline staff wrongly believed was carrying a bomb prompted a late-night emergency landing, Canadian police told AFP on Sunday.

The WestJet Airlines plane left Vancouver with 118 passengers on board but it was diverted to Thunder Bay airport late Saturday after an in-air incident and bomb squad officers were called in, police said in a statement.

"The man has a history of mental health issues. He had become agitated during yesterday's flight from Vancouver to Toronto and had to be restrained by the flight crew," and he was arrested after landing, the statement said.

The aircraft was searched overnight and "an agitated 27-year-old male passenger," was held for a medical evaluation, according to police.

"The aircraft was deemed to be safe following the search," the statement said, noting that the emergency was probably caused by language difficulties between cabin crew and the Portuguese man.

"There was a concern that he may have made utterances regarding a bomb," the statement added. "A subsequent investigation revealed a language issue."

No criminal charges will be made and it is expected that the man, along with his father will return to Portugal once a medical examination is completed, police said.

The passengers spent the night in Thunder Bay and were expected to resume their flight to Toronto on Sunday.