The House Intelligence Committee and the FBI are reportedly investigating an uncorroborated letter claiming Trump campaign adviser George Papadopoulos said he was “doing a business deal with Russians” after President Trump took office, The Atlantic reports. The letter, reviewed by the publication, was reportedly sent to Democratic Representative Adam Schiff’s office earlier this month. It reportedly states that Papadopoulos said the deal would “result in large financial gains for himself and Mr. Trump.” The author of the letter, who was not identified in the report, is also said to have claimed he witnessed a phone call between Papadopoulos and Trump in December 2016. According to The Atlantic, the individual wrote he would be willing to take a polygraph test “to prove that [he was] being truthful.” Two unnamed U.S. officials told The Atlantic the claims are being taken “very seriously.” A lawyer for Papadopoulos declined to comment. Papadopoulos is currently serving a two-week prison sentence after he pleaded guilty to lying to investigators about his 2016 interactions with Joseph Mifsud, a Russia-linked professor.