The FBI was today investigating a suspected assassination threat to US presidential hopeful Barack Obama.
A man arrested after being found with rifles, ammunition and drugs in his truck is reported to have made threats against Mr Obama, officials said.
Three other men were also arrested.
“It’s premature to say that it was a valid threat or that these folks have the ability to carry it out,” said one government official.
Mr Obama will be in Denver later this week to accept the Democratic nomination for president.
An FBI spokeswoman confirmed it was investigating the reports but would not give further details.
Tharin Gartrell (28) was arrested during a routine traffic check yesterday by police in the eastern Denver suburb of Aurora.
In his truck, officers found two rifles, including one with a scope; a bullet-proof vest; boxes of ammunition; walkie-talkies; and suspected narcotics, said Aurora police Detective Marcus Dudley.
Police alerted federal authorities, who then arrested Nathan Johnson (32) at a hotel in Denver, Mr Dudley said. A third man, Shawn Robert Adolf (33) was arrested at a suburban Glendale hotel.
Mr Adolf tried to escape by jumping from a sixth-floor window. He was hospitalised and was being held on a million-dollar bond for several outstanding warrants involving drug charges. Mr Johnson also was being held on drug charges. A fourth man is also understood to have been arrested.
Police did not say how the men were connected, but added that more arrests were possible. One of the rifles was stolen, and authorities had traced it to Kansas.
Aurora police alerted federal officials because of heightened security surrounding the Democratic convention.
“Clearly we found there are federal implications - otherwise we would not have notified them,” said Detective Dudley. “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,” he said in a statement.
Officials with the FBI, Secret Service, Bureau of Alcohol, Tobacco, Firearms and Explosives, and Aurora police are expected to release more details later today Police in Denver are trying to find out whether the reported threats to Mr Obama were valid.
“It could also turn out that these were nothing but a bunch of knuckleheads, meth-heads,” the US government official said.
AP