Japanese tech firms Sony Corp and Kyocera Corp said they have halted some production in the San Diego, California, area because of fires raging in the southern part of the state.

Sony said its headquarters office overseeing its U.S. electronics business and a small assembly facility nearby making Vaio PCs have been closed since Monday.

Both facilities were set to remain closed at least until Wednesday, and the timing for their reopening will be decided based on progress in containing the fires.

The United States represents about one quarter of Sony's electronics revenues, which came to 6 trillion yen ($52 billion) in the year ended March 31.

Electronics components maker Kyocera said it has stopped some production of chip packaging in San Diego as a number of workers have not been able to make it to the factory, which employs 500.

A Kyocera spokesman said the firm has been unable to confirm the level of production cutbacks at the plant, which mainly supplies U.S. chip makers, but so far it did not foresee shipment delays.

Kyocera's semiconductor components business posted 152.3 billion yen in sales in the past business year, accounting for 12 percent of the Kyoto-based company's overall revenues.

Sony's headquarters functions have suffered no major disruptions as people work at home using phones and e-mail, a spokeswoman said.

About 2,000 people normally work at Sony's office and the plant.

Both companies said production lines had not been damaged and no employees were hurt.

Shares in Sony closed down 1.0 percent at 5,180 yen, while Kyocera gained 0.2 percent to 9,550 yen. The benchmark Nikkei average fell 0.56 percent.