Some 21 firefighters from Lake Dillon Fire and Red, White and Blue Fire battled a “stubborn” first-alarm blaze at a house under renovation in Keystone for more than four hours on Monday night.

The unoccupied two-story home at 1337 Soda Ridge Road in the Old Keystone subdivision was fully ablaze when neighbors called 9-1-1 at 7:47 p.m., and flames from the log-beam interior had begun burning through the roof.

Crews from two ladder trucks and three engines kept the flames from spreading to neighboring houses, but the home, valued by a contractor at $2.25 million, was nearly a total loss.

“We did everything we could, but the house was too far gone,” said Lake Dillon Fire Department Deputy Chief Jeff Berino, who is leading the investigation. “This was a really stubborn fire that got into a lot of nooks and crannies. That made for a very long evening.”

The home had been undergoing a major renovation and had exposed trusses and interior walls, as well as wood finishings.

The preliminary investigation into the cause is focusing on a heating appliance in the kitchen, and foul play is not suspected.

The fire finally was brought under control at 9:22 p.m. and was declared completely out at 12:10 a.m. The owners were out of state at the time of the fire and were notified. There were no injuries.