CNN  — 

An aide to Vice President Mike Pence who listened to the call between President Donald Trump and the Ukrainian President told impeachment inquiry investigators on Thursday that she found the conversation to be unusual because it was political in nature, according to two sources familiar with the testimony.

Jennifer Williams, an aide in the vice president’s office and a long time State Department staffer, said the phone call did not have the normal tone of a diplomatic call. Williams did not raise concerns about the call with her superiors.

She was asked by lawmakers in her closed-door deposition what Pence knows and she testified that she never heard him mention anything about investigations of the 2016 election, Burisma – the Ukrainian natural gas company on whose board Joe Biden’s son Hunter sat – or the Bidens. She did not know of any request from Trump to Pence to bring up investigations during a meeting the vice president had in Warsaw with Ukrainian President Volodymyr Zelensky on September 1.

The Pence aide made note of the call and the transcript in her nightly notes but testified she did not know if the vice president read the transcript.

Pence himself has repeatedly insisted that Trump did nothing wrong but has not clarified how much he knew about efforts to pressure Ukraine and the parallel Ukraine policy that Trump’s personal lawyer Rudy Giuliani and others were leading outside the normal diplomatic and official channels.

Williams testified that she had limited information about why military aid was being withheld from Ukraine. She was puzzled about it, but was kept in the dark about the decision-making process. She described herself as someone who stayed in her lane and wasn’t pushing to understand why the aide was withheld.

However, Williams suggested to lawmakers she believed it could be tied to what she heard on the call: Trump’s request that Ukraine open investigations into the Bidens and the 2016 election, a third source familiar with the testimony told CNN.

A source with knowledge of her testimony added that Williams did not say she believed the two were connected, but simply expressed that as a possibility.

Ahead of her testimony Thursday, current and former colleagues heaped praise on Williams, with one White House official saying: “She is the most professional person in this building.”

The official noted that Williams had recently worked with Pence on negotiating the ceasefire between Turkey and Syrian Kurdish forces. Until Williams joined Pence’s staff, she was a spokesperson for several years at the US embassy in London, according to her LinkedIn profile. She also held posts at the embassies in Beirut, Lebanon and Kingston, Jamaica.

Williams’ testimony joins a stream of other government officials who have given closed-door depositions in recent weeks as House investigators continue their impeachment inquiry stemming from a whistleblower complaint about Trump’s July call with Zelensky.

CNN’s Alex Marquardt contributed to this report.