ATLANTA, Ga. -- An investigation is under way into why two boys and two girls started a fire at The Paideia School in Druid Hills Friday evening.

The school is located on a 16-acre wooded campus in the 1500 block of S. Ponce de Leon Avenue near Emory University.

Channel 2 Action News reporter George Howell spoke with a school custodian who said he noticed something suspicious as he was locking up the building.

“There were two boys and two girls. My colleague said one of the girls told the guy 'come on, let's do it and run,’” the custodian told Howell.

It appeared that the fire may have started in a stack of hay that located near the ninth grade building, also known as the Mother Goose building. Fire investigators said the hay came from a fall festival display outside the school.

"I saw straw on the street," the custodian said. "I tried to get the water hose."

A representative for Atlanta Fire-Rescue told Howell that the blaze was intentionally set.

It was unclear Friday whether the two boys and two girls who started the blaze were in custody.

Headmaster Paul Bianchi said the damaged building dates back to the 1920s. It was bought by the school in 1982.

Students and teachers gathered at the school Saturday to help clean up after the blaze.