An accidental fire at the Knights Inn in South Portland Thursday morning sent a resident to the hospital with burns and caused $200,000 worth of damage to the building, Fire Chief Kevin Guimond said.

A leaking propane heater in the room of the resident who was burned caused the fire at the inn at 634 Main St., which began about 9:15 a.m., he said. The resident also had 122 cylinders of propane in the rooms, which were exploding as firefighters battled the blaze, he said.

The man was transported to the hospital with burns on his face and hands, the chief said. He said he did not know the man’s condition.

Another resident was treated for smoke inhalation at the scene, he said. A firefighter suffered a minor shoulder injury fighting the fire, Guimond said.

The inn has about 12 to 14 rooms and has long-term guests, he said.

He said a resident was using the propane heater improperly to heat a room. Guimond said such heaters are designed for better ventilated spaces such as fishing shacks. “You’re not allowed to have propane in your home,” he said.

Charges won’t be brought because the fire was accidental, he said.

He said that about half the hotel suffered smoke, water and fire damage but firefighters managed to save the other half by cutting a hole in the roof to let the fire out. The fire was under control by 10 a.m., he said.