Officials had previously thought only two people were aboard the single-engine Piper that crashed Friday afternoon into a two-story school building Friday afternoon in the small town of Eagar.
Officials were working to identify the bodies, Apache County sheriff's Sgt. Richard Guinn said. It's not yet known whether any children were aboard the plane.
No one was in the building when the plane hit, Guinn said. There were no reports of injuries on the ground. Classes are out for the summer at the school.
The plane circled the area two or three times before it suddenly crashed into the main building at Round Valley High School at about 2 p.m., Guinn said.
Two hours after the crash, flames were still erupting 20 feet above the building. Crews worked on the blaze overnight, and the building was still smoldering Saturday.
Fire crews from nearly a dozen small towns in the region raced to battle the flames. Officials evacuated homes in neighborhoods east and north of the school.
The school serves about 500 students in Eagar and nearby Springerville and is about 200 miles east of Phoenix. The blaze was contained to the main school building.
Federal aviation officials were still trying to determine the owner of the craft.
Calls to Federal Aviation Administration and National Transportation Safety Board officials at the scene weren't immediately returned Saturday.
