Gov. Arnold Schwarzenegger declared a state of emergency Saturday for San Bernardino County, where the water supply for Barstow was found to be contaminated with a toxic chemical used to make explosives and rocket fuel.

A day earlier, Golden State Water Co. warned residents of the desert town that their drinking water contained high levels of perchlorate, a contaminant often associated with defense and aerospace activities.

Perchlorate, a type of salt derived from perchloric acid, has been found in drinking water in at least 35 states. It can interfere with iodine uptake in the thyroid gland. The thyroid, which releases hormones, helps with proper development in children and helps regulate metabolism.

Businesses close

There are similar concerns about perchlorate's effect on fetuses and newborns.

According to the governor's declaration, more than 40,000 customers were without their normal supply of drinking water, and several restaurants, hotels and other businesses had to close because of the contamination.

"My customers are worried," said George Faour, 33, who owns Barstow Liquor. "I have parents afraid that their kids are going to get sick."

Faour said residents packed into his business Friday when word spread that levels of perchlorate in several city wells had reached unacceptable levels. His customers have been stocking up on bottles and gallon containers of water.

Residents also have been flocking to grocery stores to buy water, and the Barstow Unified School District is prepared to provide students with bottled water when classes resume Monday.

Golden State spokesman John Dewey said the company began warning residents after samples taken Thursday from the water system at the nearby U.S. Marine Corps Logistics Base showed levels of perchlorate three to four times higher than the state limit.

Dewey said that company water tests Friday confirmed that the levels of the chemical exceeded standards.

Three of 20 wells in the company's Barstow system had high levels of contamination, he said. At least one of the three was operational, but it has been shut down since the discovery.

Dewey said that Golden State is trying to determine how the water supply became contaminated.

Offering bottled water

The company plans to distribute more than 100,000 bottles of water to customers in Barstow, while the system is flushed out and tested. One of the main distribution centers is Barstow Community College.

"Everything is doing a lot better. We are offering bottled water to our guests. They're not too happy, but it's still better than nothing," said Britny Gray, the front-desk clerk at the Comfort Suites hotel. "The health department says that showering is still OK."

Barstow Community Hospital has an ample supply of bottled water, and staff, patients and visitors have been warned not to drink tap water, hospital spokesman John Rader said. The hospital has drained its ice machines as a precaution, he added.

"This has affected us from an operational standpoint but not from a patient-care standpoint," Rader said. "We have been forced to make some changes."