A Uniondale school was placed on lockdown for almost two hours Wednesday while police and school officials conducted a search that turned up nothing, Nassau police said.

"You have 30 minutes to evacuate," was the message from an unknown man who called Turtle Hook Middle School on Jerusalem Avenue at 1:15 p.m., according to police and a district spokeswoman. The man hung up and school administrators immediately called police. School officials "implemented 'Shelter in Place' procedures in which students are segregated to safe zones within the school," the spokeswoman said by email.

Police conducted a building-wide search and found nothing suspicious, they said. A little less than two hours later, students were released at their normal dismissal time.

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No injuries were reported and police said the investigation is ongoing.

Anyone with information on this incident is asked to contact Nassau County Crime Stoppers at 800-244-TIPS. All calls will remain anonymous.