Canadian police are investigating a "possible hijacking" plot involving a Denver-bound United Airlines jetliner Monday.

Two unidentified men, both 23 years old and from Saskatoon, Saskatchewan, were detained by police at Saskatoon International Airport about 4 p.m. after other passengers in the boarding area overheard them talking.

"There were some comments using the word hijacking that were verbalized," Staff Sgt. Lyle Schmidt, of the Saskatoon Police Service said Tuesday.

"They were obviously not allowed to board," he said of the two men.

The flight continued to Denver International Airport after a delay, the Edmonton Sun News Web site reported.

After questioning at the police department, the men were released without charges.

"It appears that they may have been joking," said Schmidt. "It would appear there wasn't a lot of serious substance of intent, but it may not be enough to negate charges."

The two were initially headed to Denver for a hockey game, Schmidt said.

No weapon was found.

"You can be assured . . . if they had been in possession of weapons, they would not have been released," said Schmidt.

Schmidt said the case has been referred to prosecutors for possible charges under the National Aviation Act but did not say what they could be.

But, he noted, "In this day and age, you don't talk about that kind of stuff."

United spokesperson Megan McCarthy said she has little information about the incident.