National Archives officials have found as many as 5,400 records containing the pseudonyms President Joe Biden used while he was vice president, the agency said in a letter on Monday.

A search of Biden’s vice presidential records found “approximately 5,138 email messages, 25 electronic files and 200 pages of potentially responsive records” for a Freedom of Information Act request filed last year in search of three email addresses Biden was known to use to conceal his name.

A conservative group, the Southeastern Legal Foundation, filed the FOIA request and received the letter from the National Archives.

Biden used the email addresses robinware456@gmail.com, JRBWare@gmail.com, and Robert.L.Peters@pci.gov to communicate at times during his vice presidency — including, on occasion, with his son.

House Oversight Committee members pushed the National Archives earlier this month to hand over communications involving the aliases and any records that included correspondence between Joe Biden and the business partners of his son, Hunter Biden.