The US House of Representatives voted unanimously on Friday to require Director of National Intelligence Avril Haines to declassify information on the origins of Covid-19, increasing pressure on President Joe Biden's administration to allow its release.
The vote was 419 to 0 in favour. Since the Senate on March 1 passed the bill – by unanimous consent – it now goes to the White House for Biden to sign into law or veto.
The White House did not immediately respond to a request for comment on his intentions.
Washington has been conducting a highly politicised debate about the origins of the coronavirus pandemic almost since the first human cases were reported in the Chinese city of Wuhan in late 2019, amid calls from both Democrats and Republicans to push back harder against a rising China.
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The debate was refuelled last month, when the Wall Street Journal first reported that the US Energy Department had concluded the pandemic likely arose from a Chinese laboratory leak, an assessment Beijing denies.
The department made its judgment with "low confidence" in a classified intelligence report, the Journal said. Four other US agencies still judge that Covid-19 was likely the result of natural transmission, while two are undecided.
Biden administration officials have said the pandemic's origins may never be known. China said claims that a laboratory leak likely caused the pandemic have no credibility.
"The American people need to know all the aspects, including how this virus was created and specifically was the natural occurrence the result of a lab-related event?" Representative Mike Turner, the Republican chairman of the House Intelligence Committee, said as he urged support for the measure.
Representative Jim Himes, the panel's top Democrat, called the bill an important first step. "I hope it will clear up some of the speculation, some of the rumours that are out there," he said.