The campaign manager of Donald Trump’s rival for the Republican nomination, Kellner, resigned Friday amid questions about her past work for a Russian investment firm.

Kettner, a former Trump campaign adviser, was hired by Trump in October, just weeks before Trump’s victory in the New Hampshire primary, and served as his campaign manager from the end of February through the end on May 20.

She resigned Friday, according to a statement from Trump’s spokesman, Jason Miller.

“She has accepted responsibility for her actions,” Miller said.

In the statement, Miller said the campaign had hired the firm to do its due diligence and the firm had been “fully cooperating” with the campaign.

“The campaign has made clear to the firm that it will continue to cooperate with the ongoing investigation,” Miller wrote.

He did not say if the firm was being paid by Trump’s transition committee or any other entities.

On Friday, the Trump campaign did not respond to a request for comment.

The resignation comes after multiple investigations by the House Intelligence Committee and other congressional committees into Russian meddling in the 2016 election have found that Kettler and other top campaign officials engaged in “an extensive conspiracy to steal the election for the president” and to boost Trump’s chances.

The campaign has denied wrongdoing.