WASHINGTON, Sept. 20 (Xinhua) -- The U.S. Department of Health and Human Services (HHS) announced Wednesday an investment of 600 million U.S. dollars in the manufacture of new at-home COVID-19 tests and will deliver the tests for free to households across the country.

The critical investments in 12 U.S. manufacturers in seven states "will strengthen our nation's production levels of domestic at-home COVID-19 rapid tests and help mitigate the spread of the virus," HHS Secretary Xavier Becerra said in a statement.

Beginning Sept. 25, households will again be able to order four free tests through COVIDTests.gov, the agency said, adding that these tests will detect the currently circulating COVID-19 variants and are intended for use through the end of 2023.

The initiative follows four previous rounds in which the U.S. federal government and the U.S. Postal Service provided more than 755 million tests for free to households nationwide.

It is also meant to complement ongoing federal efforts to provide free COVID-19 tests to long-term care facilities, schools, low-income senior housing, uninsured individuals and underserved communities, with 500 million tests provided to date through these channels, according to the agency.