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California officials have discovered what are possibly the earliest known coronavirus deaths in the United States.

Santa Clara County announced Tuesday that three people who died at home during February and March tested positive for COVID-19 during their autopsies. The deaths took place on Feb. 6, Feb. 17 and March 6.

It was previously believed that the first US victim of the virus was a man in Washington state who died on Feb. 29.

Officials said they sent samples from the February deaths to the CDC for testing and that results came back Tuesday.

“These three individuals died at home during a time when very limited testing was available only through the CDC,” the county said in a statement.

“Testing criteria set by the CDC at the time restricted testing to only individuals with a known travel history and who sought medical care for specific symptoms.”

Santa Clara officials believe that limited testing has led to an undercount of cases and deaths, a phenomenon that has played out in other municipalities and countries, including New York City.

“As the Medical Examiner-Coroner continues to carefully investigate deaths throughout the county, we anticipate additional deaths from COVID-19 will be identified,” the statement said.