The FBI said it believes "a terror attack was disrupted" when authorities raided a western Minnesota mobile home.
The FBI arrested 24-year-old Buford Rogers on Friday, after a search of his home in Montevideo uncovered Molotov cocktails, suspected pipe bombs and firearms.
The FBI said it believes "the lives of several local residents were potentially saved" by the search and arrest.
The agency said a terror plot was discovered through analysis of intelligence gathered by local, state and federal authorities.
The statement does not offer further details about the extent or manner of the alleged plot.
Rogers is in federal custody and is charged with one count of being a felon in possession of a firearm. It is not clear if he has an attorney.
Christopher Warrener, the special agent in charge of the FBI office in Minneapolis, said: "Cooperation between the FBI and its federal, state, and local partners enabled law enforcement to prevent a potential tragedy in Montevideo."
According to a federal affidavit, FBI agents from the domestic terrorism squad searched the property at the mobile home park in Montevideo and discovered Molotov cocktails, suspected pipe bombs and firearms. The affidavit said Rogers was there at the time of the search, and one firearm recovered from Rogers' residence was a Romanian AKM assault rifle.
Rogers is expected to make his initial appearance in federal court this week.