Republicans on the House Committee on Energy and Commerce are asking the Centers for Disease Control and Prevention to investigate early possible COVID-19 cases and blood work in the U.S. to determine whether the virus was present in the country earlier than current estimates. Specifically, committee Republicans sent a letter to CDC Director Rochelle Walensky asking the CDC to use the most accurate tests available to test more blood samples from 2019 and investigate early unexplained deaths to determine if the virus was in the country earlier than December 13, 2019. The request is part of committee Republicans’ investigation into the origins of COVID-19. The Chinese government hasn’t been forthright with U.S. and international investigators, and the GOP lawmakers reason that a better understanding of when cases first arrived in the U.S. will help investigators better determine an origin timeline in China. Committee Republicans are particularly interested in whether a potential accidental lab leak led to the COVID-19 outbreak that has caused the deaths of millions worldwide. In their letter, they noted that the South China Post had tracked the first COVID-19 cases to an earlier date than the Chinese government had initially recorded. “Since the Chinese government continues to block access to pertinent data on cases in China, examination of possible evidence in the United States could shed light on the timing of when the earlier cases in China occurred,” the letter reads. The letter notes that the first SARS-CoV-2 infection was reported in the U.S. on January 19, 2020, although in November 2020, the CDC published a study that tested archived blood donations from donors in nine states between December 13, 2019, and January 17, 2020. “The results of the study indicated that it is possible the virus may have been present in California, Oregon and Washington as early as December 13-16, 2019, and in Connecticut, Iowa, Massachusetts, Michigan, Rhode Island and Wisconsin as early as December 30, 2019-January 17, 2020.” But the CDC, the letter noted, did not test blood samples from earlier than December 13, 2019. The letter said the CDC “needs to conduct additional studies to test more samples, throughout the United States, including samples several months before December 13, 2019, to gather more data to indicate how early the first case appeared in the U.S.” The Republican members asked the CDC to schedule a briefing on what it finds by June 22. CBS News has reached out to the CDC for comment. — Olivia Gazis contributed to this report.