Story highlights "We have a suspect in custody," the Royal Canadian Mounted Police tweets

The Anchorage-to-Denver flight was diverted to the Canadian city of Vancouver

Flight 1104's crew made this decision after the discovery of a threat from a passenger

(CNN) Canadian authorities detained a suspect Saturday morning after a Denver-bound United Airlines flight was diverted due to a "threatening message" found on board.

Flight 1104 departed 11:39 p.m. Friday (4:39 a.m. ET Saturday) from Anchorage, Alaska, bound for Denver, according to United's website. But "the crew elected to divert the flight after they discovered a threatening message from one of the passengers," United spokesman Charlie Hobart told CNN.

Hobart did not characterize the nature or form of the threat.

The plane landed at Vancouver International Airport, and authorities have "a suspect in custody," the Royal Canadian Mounted Police office in Richmond, British Columbia, said on Twitter.

We have a suspect in custody. @YVRairport operations unaffected at this time. More information when available. — Richmond RCMP (@RichmondRCMP) January 9, 2016

Aboard the Boeing 737 were 131 passengers and six crew members.

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