SEATTLE (AP) — Health officials in Washington state said Sunday night that a second person had died from the coronavirus.

Researchers said the virus may have been circulating for weeks undetected in the greater Seattle area.

In a statement, Public Health—Seattle & King County said a man in his 70s died Saturday. On Friday, health officials said a man in his 50s died of coronavirus. Both had underlying health conditions, and both were being treated at a hospital in Kirkland, Washington, east of Seattle.

Washington state now has 12 confirmed cases.

State and local authorities stepped up testing for the illness as the number of new cases grew nationwide, with new infections announced in California, Illinois, Rhode Island, New York and Washington state.

Authorities in the Seattle area said two more people had been diagnosed with the COVID-19 virus, both men in their 60s who were in critical condition, and two health care workers in California were also diagnosed.

A man in his 50s died in Washington on Saturday, and health officials said 50 more people in a nursing facility in Kirkland, Washington, are sick and being tested for the virus. On Sunday night, the International Association of Fire Fighters said 25 members who responded to calls for help at the nursing facility are being quarantined.

The first U.S. case was a Washington state man who had visited China, where the virus first emerged, but several recent cases in the U.S. have had no known connection to travelers.

In California, two health care workers in the San Francisco Bay area who cared for an earlier coronavirus patient were diagnosed with the virus on Sunday, the Alameda and Solano counties said in a joint statement.

The health care workers are both employed at NorthBay VacaValley Hospital in Vacaville, California, and had exposure to a patient treated there before being transferred to UC Davis Medical Center in Sacramento, the statement said. That patient was the first person in the U.S. discovered to have contracted the coronavirus with no known overseas travel.

Alameda County declared a state of emergency on Sunday following the news.

Elsewhere, authorities announced Sunday a third case in Illinois and Rhode Island and New York’s first cases as worried Americans swarmed stores to stock up on basic goods such as bottled water, canned foods and toilet paper.

The hospitalized patient in Rhode Island is a man in his 40s who had traveled to Italy in February. New York confirmed Sunday that a woman in her late 30s contracted the virus while traveling in Iran. The patient is not in serious condition. She has respiratory symptoms and has been in a controlled situation since arriving in New York, according to a statement from the governor’s office.