Kamala Harris, then vice-president elect, drove within yards of a pipe bomb left outside the Democratic National Committee on January 6 2021 and remained inside for nearly two hours before the bomb was found, it was reported on Monday.

Harris’s proximity to the bomb was known previously, but not how close or for how long. CNN reported the new details in the case, part of alarming events in Washington on the day Congress met to certify Joe Biden’s election victory over Donald Trump.

A pipe bomb was also left near the Republican National Committee. More than a year later, no suspect has been named or apprehended.

Citing “multiple sources”, CNN said Harris “pulled into DNC headquarters in Washington at around 11.30am ET with her motorcade through the garage leading to the parking deck near where law enforcement discovered the pipe bomb”.

It also cited a US Capitol police document that showed “an unnamed ‘protectee’ was removed from the DNC building at approximately 1.14pm ET – seven minutes after Capitol Police began investigating the bomb”.

That protectee was known to be Harris when Politico first reported the story, but it was not known how long she was in the building.

More than 700 people have been charged in connection with the attack on the Capitol on January 6, including 11 members of a far-right militia who face charges of seditious conspiracy. One rioter pleaded guilty to bringing with him Molotov cocktails, guns and other weapons.

The rioters attacked after Donald Trump told them to “fight like hell” in service of his lie that his defeat by Biden was the result of electoral fraud. Seven people died and more than 100 police officers were injured.

Trump was impeached but acquitted. A House committee has recommended criminal charges. Steve Bannon, a former Trump adviser, has pleaded not guilty to contempt of Congress.

The White House and Harris’s office did not comment on CNN’s pipe bomb report. A Secret Service spokesperson told CNN that “in order to maintain operational security”, it did not comment on protection arrangements.

CNN said a “law enforcement source” said the Secret Service “swept the interior of the building, the driveway, parking deck and entrances and exits prior to [Harris’s] arrival” and Harris was “evacuated using an alternate route away from the bomb”.

Earlier this month, Lis Wiehl, a former prosecutor and author of a book on the hunt for the Unabomber, told the Atlantic would-be bombers were usually “trying to send a message through killing people”.

Of the Capitol Hill pipe bomber, she said: “Because it wasn’t successful and they weren’t apprehended, you can bet they’re thinking about doing it again – and doing it better.”