Robert Scott, an office manager at Mathis' production company, said the blaze broke out on Monday evening and that he was hopeful a full assessment in the daylight would show what could be restored.
Mathis, 80, best known for the hit songs "Chances Are" and "Misty," told local television stations the fire caused extensive damage but that it could have been worst.
"Those are just things. I'm a very lucky man, I could have been here, I could have been in bed," Mathis said.
The singer had just returned to Los Angeles from performances in New York and Cleveland when he was told about the fire, which started while no one was home and was reported by a neighbor, Scott said.
Local TV station NBC4 showed firefighters standing in front of a gutted, debris-strewn room at the mansion, and Mathis wearing a baseball cap as he spoke to arson investigators.
The Los Angeles Fire Department Hosaid the cause of the blaze was under investigation and that a full damage assessment was not immediately available.
The fire damaged at least two rooms at the mansion and heat from the blaze broke glass panes on an atrium over an indoor swimming pool that sits at the center of the home, Scott said.
The fire, which also caused extensive smoke damage throughout the residence, is believed to have started in an aquarium room adjacent to the pool, he said.
Los Angeles Fire Department battalion chief Dean Zimmerman told local TV stations that firefighters had some trouble getting heavy equipment up the hill to the mansion.
"We immediately got out his trophies and some of his memorabilia that's irreplaceable," Zimmerman said. —Reuters
