The White House switchboard dialled a phone associated with a January 6 rioter after it was clear the deadly Capitol attack had failed to prevent the congressional certification of Joe Biden’s victory over Donald Trump in the 2020 presidential election, according to a new book. The book from former Republican congressman and House January 6 select committee adviser Denver Riggleman says the connection was an outgoing call routed through the switchboard at 4.34pm, and it was answered by an unnamed rioter who allegedly has since been charged by the justice department with a role in the storming of the Capitol. Riggleman’s book, titled The Breach, was reviewed by the Guardian in advance of its scheduled publication on Tuesday, and it has already become controversial after the select committee decried the work as an incomplete account that lacked information to which he was not privy once he left the panel’s inquiry in April. But in describing his work for the investigation and how he led a team analyzing call detail records, Riggleman offers previously unreported details about the White House calls around January 6 as well as the contacts around Trump’s political operatives, including Roger Stone and Alex Jones. The White House switchboard call was identified because call detail records give information about “seizure times” that indicate whether a call is answered, the book explains. In this case, the book says, there was a seizure time, indicating the call was completed. Riggleman also details other instances of connections between the White House and people connected to the Capitol attack, writing that before January 6, the president of an organization known as Latinos for Trump – closely connected to the Proud Boys group – also received a call from the White House. The Latinos for Trump president, Bianca Gracia, had a total of five connections with White House root numbers starting 202-881 or 202-456, the book said: she placed four outgoing calls and received one incoming call. The significance of the calls was not immediately clear. Sources close to the select committee have insisted that investigators chased down the leads uncovered by Riggleman and his team, but the panel could not conclusively determine the calls’ content or whether their nature was nefarious. Despite being close with the former Proud Boys national chairman Enrique Tarrio, and meeting with him in an underground parking garage near the Capitol the evening before the insurrection, Gracia was also chief of staff for Latinos for Trump. Therefore, Gracia’s calls may have been innocuous. Among other possible explanations, the sources said, was that she may have been in touch with a person on the Trump campaign or a person helping organize the Ellipse rally, or perhaps the White House may have reached Gracia when she had a tour of the complex around Christmas. The book also describes some of the sources and methods that Riggleman used to create phone link maps of “persons of interest” in the investigation, including the extensive effort to try to unravel who Stone was speaking with in the post-2020 election period. Stone was one of more than 20 “high-priority targets” but the panel faced an uphill battle identifying his contacts after he refused to voluntarily allow the select committee to obtain his call detail records, forcing investigators to work backwards through associates, the book says. The select committee was able to construct a detailed map of Stone’s contacts after obtaining the call detail records of Kristin Davis, also known as the Manhattan Madam, who was with Stone at the Willard hotel in Washington DC on the day before and the day of the Capitol attack. And after investigators identified Stone’s number, the book says, they compiled an intriguing map: Stone called Tarrio both before and after January 6, and he called the former Oath Keepers chief Stewart Rhodes nine days after the riot. Both have since been charged with seditious conspiracy. The number for Stone also connected to a number of prominent Republicans that the January 6 committee believes played different roles in Trump’s efforts to overturn the 2020 election results, including the Texas attorney general, Ken Paxton, and Arthur Schwartz, an aide to Donald Trump Jr, Trump’s eldest son. Schwartz has denied any such role. Riggleman, co-authoring the book with journalist Hunter Walker for the publisher Macmillan, also uses the book to characterize the former Trump White House chief of staff Mark Meadows as being at the center of the efforts to stop the certification of Biden’s electoral college win through the thousands of texts he provided to the select committee. Though most of the texts sent to and from Meadows that the book includes have previously been reported by CNN and others, the book fills in some gaps about the effort to object to the certification as well as the additional role played by Republican members of Congress.