A fire that started in a basement storage room caused an estimated $395,000 damage yesterday to a mansion in Potomac bought in August for $1.1 million by Lt. Col. Rifaat Assad, chief of Syria's security forces and the brother of the Syrian president.

The cause of the blaze could not be determined yesterday, according to Lt. Raymond Mulhall, public relations director for the Montgomery County Fire Department, who said there was no reason to suspect arson.

Assad bought the eight-bedroom, 13,000-square-foot Georgian colonial-style house at 9609 Halter Ct. when he was visiting the United States for a medical checkup and to enroll his two sons for the fall semester at American University.

Three members of Assad's staff were at the home when Cabin John and Bethesda firefighters arrived about 10:30 a.m. in response to a call from the house, according to fire officials. Mulhall said the fire was burning in a 12-by-20-foot storage room and it was brought under control in 30 minutes.

A firefighter was treated for smoke inhalation at Suburban Hospital.

The fire, which fed on bedding of about 20 folding cots stored in the basement, damaged basement walls and first-floor flooring and supports, shattered basement windows and spread smoke throughout the house.

When the house was bought, there was speculation that Assad, the brother of Syrian President Hafez Assad, was on a diplomatic mission in the U.S. A spokesman for Rifaat Assad said earlier this month the visit was strictly private.