Subpoenas have been sent for witnesses to testify before a grand jury in Washington DC as part of the federal investigation into former CIA Director John Brennan. According to Associated Press sources, this development is being assessed as part of the ongoing investigation into Brennan's ties to Russia and possible legal violations. Official authorities have not yet made a comprehensive statement regarding the details of the investigation and the witnesses' testimonies. Brennan's former position and the political and legal dimensions of the investigation are causing the issue to attract great public interest.