DENVER -- The Denver Water Board announced that the road on top Lake Dillon Dam was closed Thursday because of concern over recent "suspicious activity," activity that turned out to be a music video shoot.

"Recent suspicious activity on the Dillon Dam Road has prompted Denver Water and Summit County officials to close public access to the road until further notice. Officials are not commenting on the nature of the incidents but plan to assess safety and security risks at the facility early next week before determining when the road might reopen," the Denver Water Board said in a news release.

Denver Water spokeswoman Trina McGuire-Collier said she couldn't discuss specifics behind the decision to close the road.

However, the Summit County Sheriff's Office said that two men were contacted on the dam two days ago, while the road was closed as a result of adverse weather.

"Upon arrival, the deputies interviewed the two males who were from the Denver area. They stated they were filming a music video on the dam and knew that the road was closed," the sheriff's office said.

Deputies said the men were very cooperative and agreed to show them the video footage. They also agreed to have their vehicle, which was parked at the east Dillon Dam gate, inspected.

"Routine information gathered at the scene has been forwarded to the Denver field office of the FBI, which is normal protocol whenever anything suspicious occurs involving an infrastructure such as a dam. The Summit County Sheriff's Office is no longer looking into this matter," the sheriff's office said a news release.

The FBI has determined the men were not a threat, Denver FBI spokeswoman Rene VonderHaar said. She said the FBI routinely gets involved when suspicious activity is reported around infrastructure or an airplane or a train.

The Denver Water Board, which operates the dam and reservoir, decided to keep the road closed at least until next week because of the investigation.

The mile-long Dillon Dam Road runs southwest from Dillon, goes over the dam on Blue Creek, and runs along the southwest shoreline of Lake Dillon, a primary reservoir storage facility in Denver Water's collection system.

Dillon Dam is earth-filled, 5,888 feet long and 231 feet high. It can hold up to 82 billion gallons of water when full. Interstate 70 and the town of Silverthorne sit below the dam.

The 3,233-acre reservoir is a major water supply for the Denver metro area and a popular site for fishing, boating and camping.

The names of the men involved in the "suspicious activity" weren't released.

Read more about Lake Dillon on the Denver Water Web site.