Law enforcement and fire officials were investigating a potential threat on a plane at Denver International Airport on Monday afternoon, but police later said the threat was unfounded.Frontier Airlines said crewmembers discovered what they described as "threatening notes" on a plane.

Denver police Monday afternoon confirmed passengers on a flight arriving to Denver International Airport were evacuated due to a threat that "appears to be unfounded at this time."

A Frontier Airlines flight from Seattle was evacuated at Denver International Airport on Monday after crewmembers discovered two threatening notes on board, but police later determined the threat was not credible. Flight 3406 landed safely at DIA around 11:15 a.m., about an hour behind schedule.