The Secret Service and FBI have been called in to interrogate a group of men apparently preparing to assassinate Democratic Presidential candidate Barack Obama.
FBI authorities are still investigating the intention of the men, who were arrested on methamphetamine and firearms charges.
Tharin Gartrell, 28, was discovered carrying two rifles, a high-powered telescope and methamphetamine in his vehicle when he was pulled over for a routine check by a traffic policeman.
Police alerted federal authorities, who soon arrested Nathan Johnson, 32, at a hotel in Denver, Dudley said. A third man, Shawn Robert Adolf, 33, was arrested at a suburban Glendale hotel, Dudley said.
Adolf allegedly tried to evade capture by jumping from a sixth-floor window.
Marcus Dudley from Colorado police, says a number of items were seized from the car of one of those arrested.
"A bullet proof vest, two rifles, ammunition, walkie-talkies and drugs."
Aurora police alerted federal officials because of heightened security surrounding the Democratic convention, Dudley said.
"Clearly we found there are federal implications - otherwise we would not have notified them," he said.
"The weapons clearly would cause great concern."
US Attorney Troy Eid said the case was under investigation. "We're absolutely confident there is no credible threat to the candidate, the Democratic National Convention, or the people of Colorado," Eid said in a statement.
Officials with the FBI, Secret Service, Bureau of Alcohol, Tobacco, Firearms and Explosives, and Aurora police set a news conference for tomorrow.
Mr Obama has been under Secret Service protection for a year, after receiving a number of death threats.