Nassau County police found an air-powered toy gun in a student locker at Elmont High School Tuesday, ending a tense four-hour lockdown in which hundreds of students hid on the floors of darkened classrooms and cops in body armor scoured the campus for a possible gunman, authorities said.

The lockdown began after someone called 911 at 7:45 a.m. -- about 15 minutes before classes began -- and reported a "suspicious" male teenager with a backpack walking into school with a lime-green gun, police said. The caller said the object may have been a toy, police said.

Dozens of cops from elite Nassau Police units, including Emergency Services and the Bureau of Special Operations, rushed to the three-story school at 555 Ridge Rd. in Elmont and went floor to floor searching lockers, backpacks and students' clothes.

After several hours, they found a Nerf lime-green and yellow "lever action" toy gun, which fit the description given in the 911 call, police said.

The toy gun was confiscated by school officials, and will be returned to the parents of the teen who brought it to school, police said. No arrests were made.

School officials did not return calls for comment.

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Dozens of parents said they raced to the campus, thinking about the mass shooting at Sandy Hook Elementary in Newtown, Conn., last month.

When police ended their search shortly before 12:30 p.m., principal John Capozzi told about 50 parents outside the school that no one was harmed.

"At no time were any of your children ever in danger," he said "All your children are safe. I commend them. They were absolutely phenomenal."

Senior Jamie Powell, 18, said the students practice lockdown drills three or four times a year, most recently right before the Dec. 14 Newtown shooting. "In our classrooms, we turned off all the lights and hid in the back of the room, just like we learned," Powell said.

Another senior, Aren Scantlebury, 18, said, "You saw it in Connecticut, but now it's hit close to home."

Students said police officers and teachers also patted down their bodies during the search.

"It's sad that this is the new normal after Newtown," said Devon Brooks 42, who spent three hours outside the school quietly praying for his son's safety. "I've never been more fearful as a parent."

With Gary Dymski