The Justice Department and FBI are investigating American companies that worked with former pro-Russian Ukraine President Viktor Yanukovych, U.S. officials confirmed Friday evening.

While Paul Manafort, Republican nominee Donald Trump's former campaign chairman, is among the individuals being looked at, authorities said he had not been their top focus. Manafort resigned from the campaign Friday morning in what may have been in anticipation of the news.

Meanwhile across the aisle in Democratic nominee Hillary Clinton's campaign, her team chairman John Podesta, is also swimming through murky waters. John's brother, Tony, who oversees the lobbying and public relations company the Podesta Group, is also under federal agents' watch for the role his company may also have played working with pro-Russian Ukraine officials.

Ukrainian anti-corruption investigators have claimed Yanukovych and other party members ran a corrupt regime, prompting his 2014 departure to Russia.

Manafort has not responded to the breaking news. But the Podesta Group issued a statement Friday that it has hired lawyers to look into the company's relationship with a not-for-profit that had connections to the former Ukrainian regime.

"The firm has retained Caplin & Drysdale as independent, outside legal counsel to determine if we were misled by the Centre for a Modern Ukraine or any other individuals with regard to the Centre's potential ties to foreign governments or political parties," the statement said.

"When the Centre became a client, it certified in writing that 'none of the activities of the Centre are directly or indirectly supervised, directed, controlled, financed or subsidized in whole or in part by a government of a foreign country or a foreign political party,'" the statement continued. "We relied on that certification and advice from counsel in registering and reporting under the Lobbying Disclosure Act rather than the Foreign Agents Registration Act. We will take whatever measures are necessary to address this situation based on Caplin & Drysdale's review, including possible legal action against the Centre."