There were no reports of injuries on the ground. Classes are out for the summer at the school, authorities said.
The Cessna circled the area two or three times before it suddenly crashed into the main building at Round Valley High School in Eagar at about 2 p.m., Apache County sheriff's Sgt. Richard Guinn said.
Show Low Fire Department spokesman Eric Neitzel said two people aboard the plane were confirmed dead but their names and hometowns were not immediately available.
There was no immediate word on who owned the plane and where it was headed. But Neitzel said witnesses told authorities the Cessna took off from nearby Springerville Airport and experienced some sort of malfunction while it circled before veering into the school building.
Two hours after the crash, flames were still erupting 20 to 30 feet above the roof of the two-story school.
National Transportation Safety Board officials were expected at the crash scene Saturday morning to handle the investigation, according to Neitzel.
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.
There was no indication that anyone was inside the school when the plane crashed.
State Treasurer Dean Martin, who was in Eagar, said he and others left their vehicles at the school before heading out on a forest tour. They drove off just minutes before the plane hit and looked in the rearview mirro to see smoke rising into the sky.
"Initially we thought someone tossed a cigarette butt," said Martin, a state gubernatorial candidate. "But shortly after, there was this massive fireball."
A Friday night event scheduled at the high school was moved to another building.
