Attorney Jay Sekulow, a Key member of President Trump's Legal Team involving the Russian Federation probe was quoted saying they would challenge special counsel Robert Mueller if he steers the investigation into anything they consider "outside the scope" of the investigation, specifically into the President's former business deals.
Mr Flynn resigned in February, after just 24 days in the role, when it emerged he had lied to administration officials, including Mike Pence, the Vice President, about his communications with representatives of the Russian government.
On Oct. 27, White House Press Secretary Sarah Huckabee Sanders claimed the Trump administration viewed the Russian probe as "getting closer to conclusion" in an interview on Fox News' America's Newsroom.
Special counsel investigators will be interviewing witnesses this week to get more information about Flynn's lobby work as well.
Mr Manafort and his business partner, Rick Gates, were charged with 12 offences, including money laundering and conspiracy against the US. It remained unclear Sunday if Mueller had plans to pursue charges against Flynn or his son.
Flynn also was revealed to have failed to register with the Justice Department as a foreign agent for work he did during the campaign for Turkey - a felony offense.
Flynn's son, Michael G. Flynn, who worked closely with his father, accompanied him during the campaign and briefly worked on the presidential transition, could be indicted separately or at the same time as his father, according to three sources familiar with the investigation.
Barry Coburn, a lawyer for Michael Flynn Jr, declined to comment and Robert Kelner, Flynn's lawyer did not immediately respond to a request for comment. It was also unveiled that George Papadopoulos, a former Trump foreign policy adviser, pleaded guilty over the summer to lying to federal prosecutors.
If he is charged, Mr Flynn would be the fourth person to face prosecution as part of Mr Mueller's investigation.