(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.

Read More