A shooting threat forced a lockdown Tuesday morning at Tempe's Marcos de Niza High School, police said.
After the school received two calls about a possible shooting that would take place on campus, Marcos de Niza administrators decided to place the school on lockdown, Tempe police spokesman Sgt. Dan Masters said.
School staff escorted by Tempe police searched all the rooms and lockers for any evidence. No guns were found.
The school was locked down for about three hours and resumed normal operations at approximately 11 a.m., Masters said.
Masters said police are following up on the calls and trying to determine who phoned the school.