(CNN/RNN) - The Senate Intelligence committee issued a subpoena to former Trump national security adviser Michael Flynn for the release of documents tied to the ongoing Russia investigation, according to CNN.
Federal prosecutors also recently issued subpoenas to his former business associates.
Flynn is part of a larger investigation into Russia's meddling in the 2016 presidential election.
His attorney told the committee that he would not provide documents, despite a formal request in April.
Flynn is also under investigation for business dealings he had with clients tied to foreign governments.
Those financial transactions happened after he was ousted by the Obama administration from the Defense Intelligence Agency in 2014
The subpoenas are seen as a significant escalation in the investigation initially launched by the FBI last July.
Flynn resigned his national security adviser position in February after he admitted to misleading the administration about conversations he had with the Russian ambassador to the U.S.
Copyright 2017 CNN/Raycom News Network. All rights reserved.
