A US Senate committee says it obtained a backup copy of Anthony Fauci’s iPhone as it weighed whether to hold the veteran government health official in contempt of Congress for refusing to answer Republicans’ questions amid a hostile inquisition last week.

The phone was used by Fauci during his time as director of the National Institute of Allergy and Infectious Diseases, including his time fronting the first Trump administration’s response to the Covid pandemic in 2020.

Senator Ron Johnson of Wisconsin, chair of the Senate homeland security permanent subcommittee on investigations, said he had obtained a copy of the phone. “Hopefully, this device will address many of the questions he refused to answer at last week’s hearing,” Johnson wrote on social media.

The Wall Street Journal reported that the copy was transferred by the US Department of Health and Human Services, led by Fauci critic Robert F Kennedy Jr.

Last week, Fauci invoked his fifth amendment right not to testify dozens of times, and accused the Republican senator Rand Paul of Kentucky, who chairs the Senate homeland security and government affairs committee, of having an “unhinged obsession” with him.

Before the hearing, excerpts from Fauci’s journals were released to the public. They showed his growing disillusionment with Trump in the first year of the Covid-19 pandemic, when he called the president “a true embarrassment”, “totally nuts” and “truly an obnoxious adolescent”.

Johnson and Paul have sought to increase pressure on Fauci in recent days to answer questions related to pandemic health measures and the origins of Covid-19. Last week’s hearing was a continuation of Paul’s years-long support of the “lab leak” theory, or the idea that the Covid-19 pandemic began as a release from the Wuhan Institute of Virology, a theory many virologists contend is improbable.

Paul has argued Fauci’s constitutional protections did not apply during the hearing, since Fauci had received a pardon from Joe Biden. Fauci, 85, has said he fears criminal charges because Paul was trying “to get me to say something, anything, that could vindicate his repeated public pledges that I end up, in his words, ‘behind bars’”.