DENVER -- A suspect found in possession of a bulletproof vest, two rifles with a scope, boxes of ammunition, drugs and walkie-talkies is being held for investigation of possible drug and firearms violations. But the FBI is also investigating reports that he may be connected to a white supremacist group and had made death threats against Sen. Barack Obama, who will be in Denver this week to accept the Democratic nomination for president.

Aurora Police Detective Marcus Dudley said Monday that Tharin Robert Gartrell, 28, was arrested early Sunday and his arrest led to the arrest of two other suspects -- Nathan Johnson, 32, and Shawn Robert Adolf, 33.The possibility of an assassination plot is the "direction of the investigation," according to police sources.

said a U.S. government official familiar with the investigation. The official spoke on condition of anonymity because the investigation is ongoing.Dudley said Gartrell was pulled over at about 1:30 a.m. Sunday near East Hampden Avenue and South Parker Road after a sergeant noticed a truck driving erratically. Gartrell was driving with a suspended license in a rental car that was not in his name, Dudley said.The address on his license listed a home in Centennial but that is not his current address and police still do not know where he lives, Dudley said."Members of the agency are clearly on heightened alert based upon the security that's involved with a convention the size of the one that is occurring in Denver. Behavior like this can be characterized as highly suspicious. I mean, we considered that the vehicle he was driving was not listed or registered to him. It was a rental car. It was not rented in his name. He has no known address where he can be contacted here... the ammunition, the weapons -- clearly that would give one great concern," Dudley said.At least one of the rifles was stolen out of Kansas, he said. Gartrell was on probation for previous drug charges. He is currently being held at the Arapahoe County Jail on $50,000 bond, but that could change depending on further charges.The jail said he didn't have a lawyer yet but was due in court Thursday.FBI spokeswoman Kathy Wright said Gartrell is under investigation on drug and weapons charges. Wright declined to elaborate about the threat. The Joint Information Center, a command set up by Denver, state and federal authorities to field media inquiries during the Democratic convention, said it had no immediate comment.Johnson was arrested at 4:30 a.m. Sunday at a Denver hotel near Interstate 25 and Belleview. Officers with the Aurora, Glendale and Greenwood Village police departments, as well as federal law enforcement agencies, made the arrest. Johnson is currently being held in Denver on drug charges.Adolf was arrested at 5 a.m. Sunday at a Glendale hotel near Colorado Boulevard and Cherry Creek Drive South. As officers raided his room and tried to take him into custody, he jumped from a sixth-floor window of the hotel and landed on the kitchen roof, breaking his ankle, police said.He jumped off the kitchen roof and tried to run away but officers found him in the bushes nearby, Dudley said. He was taken to a nearby hospital for treatment.He had seven outstanding warrants and is being held on $1 million bond.A source in Glendale told 7NEWS that when Adolf was arrested there were indications that he may be connected to a white supremacist group. Aurora police Adolf may also be related to Gartrell.Aurora police alerted federal officials because of heightened security surrounding the DNC, Dudley said."I cannot talk about the federal implications associated with this case," Dudley said. "However, the fact that we are able to draw a nexis between this suspect and these other parties, we're extremely happy."Dudley didn't say what tied the three men together but that more arrests were possible.U.S. Attorney Troy Eid released a statement confirming the arrests had been made, but refused to comment on any possible assassination plot."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 prepared statement.Eid said he will discuss the arrests in a news conference Tuesday afternoon with officials from the FBI, Secret Service, Bureau of Alcohol, Tobacco, Firearms and Explosives, and Aurora police.Law enforcement officers in Denver are trying to find out whether the reported threats to Obama were valid."It could also turn out that these were nothing but a bunch of knuckleheads, meth heads," the U.S. government official said.