Authorities say the theft of several paintings and antiques happened a little before 3 a.m. Tuesday at Jim's of Lambertville Fine Art Gallery.
Hours later, the building was filled with heavy smoke. No injuries were reported and the extent of damage was not clear.
Officials told The Express-Times of Easton, Pa., the suspect is a white man, 6 feet tall with dark hair and wearing a long or medium-length coat.
Authorities reviewed surveillance tapes and determined he did not cross the bridge from Lambertville to New Hope, Pa.