Hawaii Island firefighters could not determine the cause of a fire that damaged a modular home Saturday in Puna.

The fire started about 4:10 a.m. at 11-2000 Jungle King Avenue in the Fern Forest subdivision, firefighters said.

Arriving firefighters saw flames in one section of an unpermitted, single-story module-type home with the metal roof partially collapsed. A woman staying in the home was already outside.

Firefighters extinguished the fire in the 144-square foot bedroom. No one was hurt.

Damage was estimated at $500.