As many as 100 people may have fallen for a scam involving deeply discounted airline tickets from Toronto to Las Vegas for an upcoming conference.

WestJet Airlines reported Monday that it had uncovered a scam involving purported WestJet fares discounted by as much as 50 per cent than fares available through its own website.

After customers paid the airfare, they discovered their ticket was invalid.

The deal was offered on Facebook to attendees of a particular conference, which WestJet has not named.

WestJet said its own fraud investigators discovered the problem, because the credit cards used to buy the tickets were stolen. The Calgary-based airline said a fraud team regularly monitors its transactions.

"It's estimated as many as 100 conference registrants accepted the offer and paid for airfare only to discover that their ticket was invalid because it was purchased with other individuals' stolen credit cards," WestJet said in a statement.

“We noticed these purchases, because they were made with Discover credit cards, and we don’t normally see as many of those as larger, more common cards such as Visa and MasterCard,“ said WestJet spokesman Robert Palmer in an email to CBC News.

"All of these fraudulent purchases have been refunded."

Palmer said Toronto police are continuing the investigation.

WestJet advised customers to avoid suspicious-looking deals advertised online and to book flights directly with the airline, a travel agent or reputable travel service provider.