Fire Chief Steve Gorrell said evidence found at the scene confirmed the blaze was arson. He declined to disclose details, citing the ongoing investigation.
``We know how it started, it's just a matter of finding out who started it,'' Gorrell said. ``It appears to be arson.''
Fire investigators were working with the company to obtain a list of employees who were in the factory at the time of the fire.
Workers at the Thomson SA-owned plant had been anticipating a full or partial shutdown for months as production downsized and crews moved equipment out of the 1.2-million-square-foot plant.
About 865 hourly and 125 salaried workers were affected by the decision, which the company blamed on weak sales.
Thomson, which is based in Paris, employs 50,000 worldwide and 10,000 in the United States. It markets the RCA brand of electronics in North America and Thomson brand in Europe. It markets both in Asia.
In trading Wednesday, U.S. traded shares of Thomson were up 75 cents to close at $18.52 on the New York Stock Exchange.
