UPPER MARLBORO, MD - A roller coaster at Six Flags in Upper Marlboro, Md. near Washington, DC. (Lance Rosenfield/Prime/Lance Rosenfield)

Six Flags America was evacuated Saturday afternoon after an unspecified phone threat, but a security sweep of the Upper Marlboro amusement park turned up nothing suspicious, Prince George’s County police said.

The park will remain closed for the day and evening, said Lt. David Coleman, a police spokesperson.

The threat was received at about 1:30 pm and an evacuation was started shortly after “out of an abundance of caution,” Coleman said, while investigators assessed the“source and validity” of the threat. He declined to elaborate on the nature of the message.

No injuries were reported.

The sweep of the park was completed at around 4:30 p.m., police said.

Six Flags spokesperson Debra Evans said in an e-mailed statement that the park will open as scheduled Sunday from 10:30 am to 6:30 pm.

This was the second threat directed at Six Flags in the last two months. The park was emptied on July 13 after a supervisor received a text message about bombs.

Security personnel found two unattended backpacks that contained nothing explosive.