DAYTONA BEACH, Fla., Sept. 11 (UPI) -- Four suspects on a terror watch list were seen driving past the Daytona International Speedway and taking pictures of the Florida track, police sources say.

The incident, which occurred last July during one of the busiest weeks of the racing season, is part of an open investigation, federal, state and local officials said, Central Florida News reported Friday.

The cable news station says most information surrounding the event remains secret but Daytona Beach police have confirmed some details.

"Florida Highway Patrol saw a suspicious vehicle with four gentlemen taking pictures of the speedway," Deputy Chief Stephen Beres told Central Florida News.

Beres said normally that wouldn't be an issue but the men denied they were taking pictures after being stopped by authorities who confiscated their camera's memory card.

Central Florida News says sources told them the names of the four men in the car turned up a terror watch list.