The head of a House oversight panel on Monday renewed its investigation into political interference in the nation’s coronavirus response, releasing new allegations of meddling in scientists’ work.

Rep. James E. Clyburn (D-S.C.), chairman of the House select subcommittee on the coronavirus crisis, released emails from a Trump science adviser that he said showed how the administration worked to weaken guidance on who should be tested for the coronavirus. Clyburn also cited evidence that Trump appointees sought to boost access to unproven treatments for the coronavirus that were favored by the president.

The panel “is continuing these critical investigations … in order to understand what went wrong over the last year and determine what corrective steps are necessary to control the virus and save American lives,” Clyburn wrote to White House Chief of Staff Ron Klain and acting health and human services secretary Norris Cochran, in letters shared with The Washington Post.

Clyburn said the Trump administration had blocked the subcommittee’s inquiries, noting that HHS officials “failed to fully comply with two subpoenas and at least 20 document requests.”

Clyburn’s latest allegations focus on emails sent last year by then-scientific adviser Paul Alexander, a Trump appointee who repeatedly clashed with career scientists — and called for deliberately infecting younger Americans with the virus, arguing that it would speed “herd immunity” — before being fired in September. Alexander did not immediately respond to an email request for comment.

In one of the newly released emails, Alexander defended a controversial decision by the Centers for Disease Control and Prevention to abruptly revise its guidance to reduce the number of people getting tested for coronavirus.

Under that revised guidance issued last August, the CDC said that Americans who had been in close contact with infected people but did not have symptoms “do not necessarily need a test.” According to Alexander, the White House supported the decision because the prior strategy was posing a risk to efforts to reopen the economy — a major priority for President Donald Trump in the run-up to last year’s election.

“Testing asymptomatic people to seek asymptomatic cases is not the point of testing,” Alexander wrote in an Aug. 27, 2020, email obtained by the panel, adding that “all this accomplishes is we end up quarantining asymptomatic, low-risk people and preventing the workforce from working.”

The CDC in September reversed its guidance on asymptomatic testing, following a torrent of complaints from public health experts who said it was necessary to uncover hidden cases of the virus, which were helping to drive the epidemic. Officials at colleges like Duke University cited such testing as a crucial element in schools’ ability to reopen last year.

The panel also released emails in which Alexander repeatedly appealed to health officials to increase access to hydroxychloroquine, the anti-malaria drug touted by Trump as a coronavirus treatment despite evidence it was ineffective. Amid White House pressure, the Food and Drug Administration authorized the drug in March 2020 to be used for patients hospitalized with the coronavirus, before revoking the authorization in June and subsequently warning about the drug’s risks. Trump complained about the FDA’s reversal, and appointees like Alexander urged the agency to reconsider.

In one email sent July 19, 2020, to then-FDA Commissioner Stephen Hahn and then-FDA deputy commissioner Anand Shah, Alexander shared draft data from a “highly confidential” analysis scheduled to be published in the British Medical Journal. According to the draft data, which Alexander had obtained as a participating researcher, patients who received the malaria drug as part of their treatment regimen had “a shorter symptom duration than standard care.”

“I would never do this but do it here for we have lives on the line, and we are searching for a treatment or combination. and I want to help the administration and you two as the top regulators in this push,” Alexander wrote to the FDA officials. “[W]e are being fought by the other side and media, which is horrendous for we have a very serious emergency.”

However, the final analysis published by the British Medical Journal on July 30, 2020, concluded that there was “no evidence” that the hydroxychloroquine treatment combination reduced patients’ symptoms compared to standard care.

In another email sent Aug. 18, 2020, to colleagues in the health department’s press shop, Alexander critiqued Anthony S. Fauci, the government’s leading infectious-disease expert, for his public criticism of hydroxychloroquine as a coronavirus treatment.

“This is not a medical or public health issue, but now a political issue, because the President said good things about it,” Alexander asserted. “[H]ad he not, this [hydroxychloroquine] would be standard of care.”

In his letter to HHS, Clyburn calls for documents sent by at least 46 current and former health department officials, ranging from Trump appointees like former HHS secretary Alex Azar, to career civil servants working on the coronavirus response. The Trump administration last year mostly limited its document releases to emails sent by Alexander, said a subcommittee aide familiar with the probe.

Clyburn on Monday also said that the administration “failed to provide a meaningful response” to his panel’s requests for documents on the Trump administration’s vaccination strategy.

The White House said it was reviewing the panel’s requests.

“We appreciate Chairman Clyburn and the Select Subcommittee’s diligent work to help ensure an effective, science-driven pandemic response on the part of the United States government,” spokesperson Kevin Munoz said. “The White House is focused on vaccinating the U.S. population efficiently and equitably and slowing the spread of covid-19.”