Six Flags Magic Mountain was locked down early Monday after deputies responded to a bomb threat report at the Valencia, California, theme park around 7:55 a.m. The park was closed to visitors when the call came in, but employees who were inside were evacuated as deputies swept the grounds.

California Highway Patrol officers helped with traffic control and secured entrances while sheriff’s deputies searched the property. Authorities shut down the main entrance on Magic Mountain Parkway and the employee entrance near Sky View Lane and Feedmill Road, and aerial footage showed several sheriff’s vehicles near the gate as the search continued.

The park said it was aware of the police activity and was monitoring the situation with local authorities. Video from local television helicopters also appeared to show an armored sheriff’s vehicle and a fire engine on scene, underscoring how quickly the response escalated at a place that ordinarily opens from 10:30 a.m. to 6:00 p.m.

The sheriff’s office said just before noon that the park had been cleared and was safe. Officials said the reported threat was not credible and that there was only one call, and no injuries were reported.

That left the park closed well past its scheduled opening time Monday morning while deputies finished their investigation. For families heading to the amusement park, the question was not whether the gates would open on time — they already had not — but how quickly authorities could rule out danger and restore normal operations.