Two people were arrested, while three others were questioned, law enforcement sources told NBC News.
They were all reportedly naturalised US citizens, from an unidentified Middle Eastern country, who had access to firearms and firearms training.
Following the arrests, Jordan Hall, an FBI spokesman in Detroit, said: “There is no current threat to public safety.”
Hallowe’en reference prompted FBI to act
FBI and state police vehicles thought to be involved in the investigation were seen in a neighbourhood near Fordson High School in Dearborn, a district of suburban Detroit. Personnel wearing FBI shirts were spotted entering a house and carrying evidence bags.
It was not immediately clear if the suspects had the means to carry out an attack, but the reference to Hallowe’en prompted the FBI to make the arrests on Friday, a source told the Associated Press.
Sources said the group had been tracked leading up to the arrests.
It was not clear if any specific targets for the attack had been identified.
Gretchen Whitmer, the governor of Michigan, wrote on X:
