DENVER — The FBI is looking into reports in Denver media outlets that a man under investigation for drug and weapons violations may have made threats against Senator Obama, officials said today.

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

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

An FBI spokeswoman, Kathy Wright, confirmed the FBI was investigating the reports but declined to elaborate. 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.

An Aurora Police Detective, Marcus Dudley, said today that a 28-year-old, Tharin Robert Gartrell, was arrested early yesterday in a routine traffic stop in the Denver suburb of Aurora. He is being investigated for possible methamphetamine and firearms violations, officials said.

Two other people were arrested in the case, Aurora police said in a statement. They didn’t immediately release more details.

Law enforcers 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 American government official said.

Mr. Gartrell was being held at the Arapahoe County jail on $50,000 bail on a felony charge of special offender, drug violations. The jail said he didn’t have a lawyer yet but was due in court Thursday.

U.S. Attorney Troy Eid said in a statement that federal charges were anticipated. Mr. Eid did not elaborate, but officials with the FBI; Secret Service; the Bureau of Alcohol, Tobacco, Firearms and Explosives, and Aurora police set a news conference for tomorrow afternoon.