Denver ? Federal authorities are looking into reports that a man arrested with rifles, ammunition and drugs in his truck may have made threats against Barack Obama, officials said Monday.

Two other men were arrested in the case.

“It’s premature to say that it was a valid threat or that these folks have the ability to carry it out,” said a U.S. government official familiar with the investigation. The official spoke on condition of anonymity because the investigation is ongoing.

Obama will be in Denver later this week to accept the Democratic nomination for president.

Tharin Gartrell, 28, was arrested during a traffic stop early Sunday by police in the eastern Denver suburb of Aurora. In his truck, officers found two rifles, including one with a scope; a bulletproof vest; boxes of ammunition; walkie-talkies; and suspected narcotics, said Aurora police Detective Marcus Dudley.

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.