A fire broke out at New Milford High School Tuesday. 

Crews say the fire was on the roof, extending into a third-floor classroom.

More than 100 first responders arrived on the scene Tuesday afternoon.

Six firefighters were treated for minor injuries. 

Part of the school has severe water and smoke damage, and the area of the roof that was burned is having an emergency patch put in place due to the impending rain.

The cause of the fire is under investigation.