An HBO movie set in Ellenville went up in flames overnight .

A massive fire tore through a used car dealership on Route 209 around 1 a.m.

The set is where actor Mark Ruffalo and actress Melissa Leo just started shooting an HBO miniseries called, "I Know This Much Is True."

Production was not in progress when the fire broke out, but film security was on site and reported the fire.

Fire departments from across Ulster, Orange and Sullivan counties were called in to fight the flames.

Firefighters believe the fire broke out in the repair shop of the dealership and spread. Fighting the fire was dangerous because of explosions due to a number of accelerants on site.

Crews used heavy machinery to clear the debris, including a number of antique cars that were at the dealership for the film shoot.

No injuries have been reported.