A fire at a dental office in Fontana early Thursday morning has been determined to be just one in a string of related arson fires.
San Bernardino County fire investigators say that blaze is tied to three other fires set at dental offices in March, according to a news release.
All four fires occurred along Sierra Avenue in Fontana and the arsonist used similar ignition sources.
The latest fire occurred at the Western Dental office in the 10100 block of Sierra Avenue at approximately 3:22 a.m.
Heavy smoke was billowing from all sides of the 3,100 square-foot structure and had been burning for a while before it was spotting by a passing motorist.
Firefighters extinguished the flames within a half hour and were able to contain the fire to the rear of the structure where it originated.
Due to the type of equipment and materials inside the building, heat radiated throughout, melting just about everything inside the business.
Damage is estimated at over a million dollars.
Fire investigators are conducting the investigations with the assistance of the Fontana Police Department.