The historic residence of the late U.S. architect Jay H. Morgan in Fujisawa, Kanagawa Prefecture, was almost completely gutted Wednesday morning in a suspected arson attack, police said.
No one lives in the house and there were no reported injuries. An adjacent building was also gutted.
The two-story wooden house was undergoing restoration after being severely damaged last May by another fire, also a suspected arson.
Morgan was a prominent architect who came to Japan in 1920 to help design the now-demolished Marunouchi Building near JR Tokyo Station, as well as other well-known buildings. He lived in Japan until he died in 1937 at age 63.
He built the chic Western-style Fujisawa residence known for its orange roof tiles in 1931 as his home.
Citizens' groups have been engaged in efforts to preserve the home, and were trying to restore the sections damaged by last year's fire.
"I'm at a loss for words. I can't think of what to do to rebuild the house," said Junko Tokushige, a representative of a group to preserve the Morgan residence, after she rushed to scene.
Police said a neighbor alerted the fire department at around 5:30 a.m.
Flames were first witnessed at the separate building, which is more than 10 meters away from the Morgan house, and then at the house about 30 minutes later, they said.