One of Vice President Mike Pence’s senior staffers is likely to testify in front of House impeachment investigators, according to CNN.

Anonymous sources told CNN on Tuesday that Jennifer Williams, an adviser on Pence’s national security team, will probably comply with the investigators’ request for a deposition on Thursday.

An unnamed White House official also told CNN that unlike Pence, Williams was on the infamous call between President Donald Trump and Ukrainian President Volodymyr Zelensky in July. The Washington Post reported in October that Pence’s other national security adviser, Lt. Gen. Keith Kellogg, was also on the call.

According to the Post, Pence would’ve had access to a transcript of the call “within hours” after it ended.

Williams also accompanied the vice president on his trip to Warsaw, Poland on September 1, where he met with Zelensky directly and discussed Trump’s withholding of military aid to Ukraine. Pence later told the press he had raised the administration’s “great concerns” on the issue of corruption with Zelensky, though he denied bringing up Joe Biden and his son Hunter.