Five days before the first slaying, a police officer in Gulfport noticed an unoccupied 1990 blue Chevrolet Caprice with New Jersey license plates.
At the time, the officer found nothing suspicious when he ran the car's plate through the National Crime Information Center network.
The car was owned by Muhammad, who is now accused of killing 10 people with a rifle and injuring three others in Washington, D.C. suburbs.
Muhammad's traveling companion, 17-year-old John Lee Malvo, also is being held in connection with the killings.
Gulfport's information has been turned over to the FBI to verify the travel of the two sniper suspects, who were captured Thursday.