At least two computers were stolen from the Capitol when a violent mob of Donald Trump supporters stormed the building on Wednesday – including one from the office of the House speaker, Nancy Pelosi – raising grave information security concerns. An aide to Pelosi confirmed Friday that a laptop was stolen from the speaker’s office, saying it belonged “to a conference room and was used for presentations”, but did not elaborate further on what information it may contain.

At least one other computer was stolen, a laptop belonging to the office of the Democratic senator Jeff Merkley, of Oregon. The acting US attorney, Michael Sherwin, said that some of the thefts might have potentially jeopardized what he described as “national security equities”.

The theft of electronic devices from congressional offices has been a persistent worry following the invasion by Trump supporters, who, incited by the president, entered the capitol in an effort to subvert the certification of Joe Biden’s election win.

Staffers were quickly forced to shelter in place, leaving many devices vulnerable to the attackers. Photos posted by rioters from inside the Capitol showed exposed computers, including one in Pelosi’s office with an email inbox in full view. The impact of such a device being taken could be grave, said Brandon Hoffman, the chief information security officer at IT security provider Netenrich.

“Regardless of how much they want to downplay this, the laptop has to have at least access that could be leveraged,” he said. “It’s highly unlikely that this laptop was sitting there with no files, or file access, or any other useful information to somebody looking for leverage or retribution.”

What else might have been taken during the chaos is not yet known. Some information technology experts worry that intruders may have planted malicious software on computers, although it’s not clear that devices were a particular focus of the attack.

The concerns come as the US grapples with the aftermath of the biggest state-sanctioned hack of the government in history, after SolarWinds was breached and government email was accessed. Officials are still working to determine the extent to which government devices were violated in that breach, which is now being attributed to Russia. Nearly 10 agencies were impacted, including the US Treasury and Department of Commerce.

Donald Trump’s deputy national security adviser, Matt Pottinger, and former chief of staff and current special envoy to Northern Ireland, Mick Mulvaney, have resigned. Two other senior White House officials – the national security adviser, Robert O’Brien, and the deputy chief of staff, Chris Liddell – are reportedly considering stepping down after a mob of Donald Trump supporters stormed the US Capitol building.

Pottinger and Mulvaney’s departures comes amid speculation that others will also quit after the US president incited and praised rioters while continuing to air baseless grievances over his loss of the presidency.

“I called [Secretary of State] Mike Pompeo last night to let him know I was resigning from that. I can’t do it. I can’t stay,” Mick Mulvaney told CNBC on Thursday morning.

“Those who choose to stay, and I have talked with some of them, are choosing to stay because they’re worried the president might put someone worse in,” Mulvaney added.

So far seven officials associated with Trump and his inner circle have said they are quitting, including members of Melania Trump’s team, after the deadly violence that surrounded the Congressional vote to certify Joe Biden’s presidential election victory in November.

Senior Republican figures have also indicated splits from the president.

Tweeting from his personal account, O’Brien – a staunch Trump loyalist – praised the behaviour of the vice-president, Mike Pence, who resisted Trump’s pressure to overturn the election certification, while making no mention of Trump.

“I just spoke with Vice President Pence. He is a genuinely fine and decent man,” he tweeted. “He exhibited courage today as he did at the Capitol on 9/11 as a Congressman. I am proud to serve with him.”

In further fallout that underlined the fracturing of the Trump administration’s inner circles, Marc Short, Pence’s chief of staff, indicated to journalists he had been banned from the White House by Trump after the president “blamed” him for advice he gave to Pence on Trump’s demands he overturn the election result.

According to reports in the US media, some senior administration officials have also begun talking informally about invoking the 25th amendment to remove the president before his term expires on 20 January, while calls are also growing for a second impeachment to ensure Trump cannot run for public office again.