ABC News' Jason Ryan, Richard Esposito, Pierre Thomas, Jack Date, Mary Compton and Theresa Cook Report: Federal and local authorities in Colorado are questioning several suspects to determine if one of the men made a threat against Sen. Barack Obama, who will be in Denver this week to accept the Democratic presidential nomination.After pulling over Tharin Robert Gartrell, 28, for allegedly driving erratically early Sunday morning, police discovered two rifles, one of which is reportedly stolen, a scope, a bulletproof vest, ammunition, walkie-talkies and the drug methamphetamine in the rented 2008 Dodge Ram truck, Aurora Police Detective Marcus Dudley said at a Monday evening press conference.When authorities questioned Gartrell about the findings, he pointed to an associate of his whom he claimed made a threat against Obama, officials told ABC News.According to law enforcement sources in Denver, a witness interviewed in the case told investigators that one of suspects allegedly said the guns were to be used to kill the Illinois senator, but authorities do not believe the alleged threat put Obama in immediate danger.At approximately 4:30 a.m. Sunday, police arrived at a Glendale, Colo. hotel to question another suspect, who jumped from a sixth-floor window in an attempt to evade police. Medical personnel at a Denver area hospital treated him for a broken ankle. Police arrested both Nathan Johnson, 32, and Shawn Robert Adolph, 33, in connection with the investigation. All three men are in the custody of law enforcement authorities, and all have criminal records, officers said at the press conference.Authorities told ABC News the men had tattoos of white supremacist images.State, local and federal investigators are working together to decide which charges they will file against the men. Federal authorities scheduled a Tuesday press conference, and noted that prosecutors anticipate filing federal charges as part of the case."This is a methamphetamine and firearms case that arose from a traffic stop made by an Aurora Police officer," a spokesman for the joint law enforcement information center told ABC News. "Firearms and methamphetamines were seized, and a number of individuals are in state custody. The matter continues to be under investigation. We'll provide more information as it becomes available."The Obama campaign declined to comment on the situation.The incident comes on the heels of an alleged threat against Obama's rival, Sen. John McCain, R-Ariz. Last Friday, prosectuors charged an inmate at the Arapahoe County, Colo. jail for allegedly mailing a threatening letter laced with powder to the McCain's Denver campaign office. Investigators later determined that the suspicious powder was not toxic.ABC News' Sunlen Miller contributed to this report.