UPDATE: Students returned to their classrooms this afternoon after Scottsdale police deemed the campus safe. It's unclear whether there ever was an armed man on Cocopah Middle School's grounds, but police still deem the tip serious.
Cocopah Middle School in Arizona is on lockdown and students were kept off campus after a nearby food-service worker reportedly saw an armed man on school grounds.
ABC 15 reports that the food-service worker saw a man with a long coat and a holstered weapon at about 6 a.m. The claim remains unconfirmed, but police barred students from entering the school and are searching the grounds, room by room.
Scottsdale police Sgt. Mark Clark said the report appeared to be credible, but authorities have not found any evidence of a shooter as of 11 a.m., Fox 10 reports.
"We're searching every building, every square inch of the campus," Clark told AZFamily.com. "We want to make sure there is absolutely nobody on campus who isn't supposed to be here... We want to make sure it's safe before we let anyone back here."
The American flag at the middle school is still flying at half mast in honor of the victims of Friday's deadly mass shooting at Sandy Hook Elementary School in Newtown, Conn.