A gas odor from two air units forced a Gwinnett County elementary school to briefly evacuate Wednesday morning after the gas smell was noticed inside the building.

Firefighters were sent to Magill Elementary School on Brushy Fork Road near Loganville after being alerted to the smell by a school administrator, Gwinnett fire Capt. Tommy Rutledge said.

"Firefighters have detected only slight gas readings on their monitors, but have no active odor of gas at this time," Rutledge said shortly after 11 a.m. "As a precaution, the students are evacuated to the outside until the source can be located."

The source of the smell was two air handling units on the roof, Rutledge said Wednesday afternoon.

The students were allowed to return inside the building around 11:30 a.m.

-- Alexis Stevens contributed to this report.