The House select committee investigating the Capitol attack revealed on Thursday that it had evidence to suggest certain “reconnaissance tours” took place in the days before 6 January, potentially providing some rioters with a layout of the complex.

The panel said in a letter requesting cooperation from Georgia Republican congressman Barry Loudermilk that he gave a tour the day before the Capitol attack. The startling disclosure resurrects a contentious line of inquiry that connects House Republicans to the insurrection.

“Based on our review of evidence in the select committee’s possession, we believe you have information regarding a tour you led through parts of the Capitol complex on Jan 5, 2021,” said a letter from Bennie Thompson, the chairman of the select committee, and the vice chair Liz Cheney.

The select committee noted in the letter to Loudermilk that Republicans on the House administration committee that reviewed security camera footage of the Capitol before January 6 recently claimed there were no tours or large groups or anyone wearing Maga caps.

“However, the select committee’s review of evidence directly contradicts that denial,” Thompson and Cheney wrote.

The request for voluntary cooperation from Loudermilk indicates the panel has been quietly focused on one of the unexplained mysteries of 6 January: how certain supporters of Donald Trump who stormed the Capitol appeared to know in advance the layout of the Capitol complex.

Some of the offices and ceremonial spaces in the Capitol – such as House Speaker Nancy Pelosi’s office – are marked and easy to locate. But Democrats raised concerns after 6 January that some rioters were able to locate hideaway offices and the underground tunnel network.

The concerns led to 34 House Democrats seeking an investigation into the alleged reconnaissance tours that took place on 5 January 2021, which prompted a review of security camera footage by the House administration committee, according to two sources familiar with the matter.

Democrats on the House administration committee turned over some of that footage to the US attorney for the District of Columbia, which is prosecuting January 6 seditious conspiracy and obstruction of Congress cases, the sources said.

But the top Republican on that committee said in February that some of his members had reviewed the footage and said in a separate letter that “it does not support these repeated Democrat accusations about so-called ‘reconnaissance’ tours”.

In a twist, Loudermilk filed an ethics complaint last May against Democratic congresswoman Mikie Sherrill and other Democrats who alleged GOP members had given such tours.

“No Republican member of Congress led any kind of ‘reconnaissance’ tours through the Capitol, proven by security footage captured by the US Capitol police,” Loudermilk said as part of his complaint that urged the House ethics committee to investigate Sherrill.

The select committee investigating 6 January events reached a different conclusion, Thompson and Cheney wrote, and identified Loudermilk as among the members who provided tours the day before the Capitol attack – at a time when congressional Covid-19 rules prohibited such tours.