An Air Canada jet came off the runway after landing at the Halifax airport in Nova Scotia on Sunday, sending at least 23 people to hospital, officials said.

The airline said earlier on Twitter that flight AC624 from Toronto "exited runway upon landing at Halifax."

Police arrested an American biochemistry professor at an Ottawa hotel Wednesday over an alleged chemical threat that prompted authorities to evacuate the building, police and media reported.

"We apprehended a male at the Chimo hotel without incident," a police spokeswoman told AFP.

Canada has expelled four Russian diplomats following the arrest last weekend of a Canadian soldier charged with leaking secrets to a foreign entity, a newspaper reported Friday.

Canada's Globe and Mail said the four diplomats had been removed from the list of envoys officially recognized by Canada, while the CBC news service said at least some of them had left the country over the spying case.