This is one of the firefighters who worked to identify the cause of smoke Tuesday at Mars High School. Students and teachers were ushered to Mars Middle School, across Route 228, in the interim.

ADAMS TWP — About 1,000 students were evacuated from Mars High School for two and a half hours Tuesday after a malfunctioning heater caused smoke to fill the halls.

The smoke came from a motor that had burned out. The building’s ventilation system then carried smoke through the building, said Superintendent Jim Budzilek.

After being alerted to a “haze” throughout the building, school officials decided to evacuate the building about 11 a.m., Budzilek said.

With assistance from emergency responders, the teachers and students were escorted to Mars Middle School on the other side of Route 228.

Parents were alerted of the incident by e-mails and an automated phone message, he said.

Firefighters and employees of Schulz Heating and Cooling located the burned-out motor in a wrestling room. “It was isolated in a small boxed-in area that was tough to find,” Budzilek said.

They removed the malfunctioning unit and used portable fans to clear the building of smoke.

The students waited in the gymnasium, cafeteria and commons area of the middle school while officials assessed the situation at the high school.

About 12:30 p.m. Adams Fire Chief Bill Hayes turned the building back over to school officials. Police and firefighters helped escort the students back across the road to resume classes about 1:30 p.m.

Budzilek thanked principal Todd Kolson and all the responders for making the response to the incident go as smoothly as possible.

“I can’t thank local firefighters, local law enforcement, school administrators and the heating company enough,” he said.