A man who served as a translator for Michael Cohen while he brokered a deal with Korean Aerospace Industries was recently interviewed by the FBI, signaling federal investigators are interested in the the $150,000 payment Cohen received from the company, according to the Washington Post.

The translator, Mark Ko, who lives in California, told the Post that he had been interviewed by FBI agents about the contract “a few weeks ago,” but would not provide details about the interviews. Ko told the Post that he didn’t know if the agents were members of special counsel Robert Mueller’s team.

Korean Aerospace Industries is one of several companies — like AT&T and drug company Novartis — that’s been questioned by federal authorities over its payments to President Donald Trump’s personal attorney after the 2016 election. AT&T and Novartis have both confirmed they went into business with Cohen, through his shadow consulting company Essential Consultants, because Cohen sold them access to Trump and his policy makers.

Novartis paid Cohen $1.2 million over the course of a year and AT&T spent $600,000 to work with Cohen. Both companies have expressed regret for the decision and have ousted top executives over the matter.

The South Korean aerospace company, on the other hand, has defended its contract with Cohen, saying it didn’t know about Cohen’s relationship with Trump and went into business with him to get legal advice on U.S. accounting procedures.