Stonington — Remains of the Ram Island house destroyed by fire Friday were still too hot to handle Saturday.

"We're trying to let it cool down a day," Stonington Fire Marshal George Brennan said. "It's a big pile of hot ashes. There's not much digging we can do until it cools down."

Brennan said the cause of the blaze was "under investigation."

Firefighters traveled by boat to the private island off Mystic after smoke was spotted there Friday afternoon. The house, which was not occupied at the time, could not be saved.

Fire destroyed a barn on the island on Feb. 20, 2013.

"It's kind of no man's land," Brennan said of the island, which is owned by John Ragsdale. "It doesn't belong in any (Stonington) fire district. It's probably the only piece of land in town that doesn't pay taxes to any fire district."

That circumstance, Brennan said, had no effect on firefighters' response to the fire.

Firefighters from Mystic, Noank, the Quaimbaug Fire Department in Stonington and Groton Long Point responded. The Mystic and Groton Long Point departments provided boats.

Brennan said he and Detective Sgt. David Knowles of the Stonington Police Department would investigate the cause of the fire.