"The city wide arson task force has determined this fire was incendiary. This fire will be investigated as an arson," said Special Agent John Hageman of the ATF.
The fire was located in a ground floor classroom in the back of the Germantown Jewish Centre. Teachers in another class discovered the flames early Friday morning.
"One teacher looked down hallway and saw flames coming from the classroom. She went down and saw flames in the classroom," said Lt. Wayne Forte of the Philadelphia Arson Task Force.
An ATF dog did not detect any accelerants. Authorities believe the fire was set with paper, wood from shelving and plastics.
Investigators are trying to determine if the fire is linked to some swastikas that were drawn on the back of the building two weeks ago.
The drawings are gone now, but the scars are apparent in the hearts of people like Cherie Goren, a member of the synagogue for 55 of its 57 years in existence.
"Growing up in Europe under Hitler, it evokes bad memories," said Goren.
The fire destroyed Linda Rich's class. She salvaged some preschoolers' drawings of dreams done for Martin Luther King Jr. Day.
"I feel sad and scared. I feel like, when is this going to stop," she said.
The team of police, fire and ATF investigators is trying to determine who set the fire and whether they had a hand in the hate crime vandalism.