House Democrats said late Thursday that they are investigating Vice President Mike Pence's actions as part of their impeachment inquiry into President Donald Trump's efforts to press Ukrainian President Volodymyr Zelensky for damaging information on Joe Biden.

The chairmen of three House committees leading the investigation said in a joint letter that new reports have revealed that other Trump administration officials "may have been involved in the illicit effort to get Ukrainian help for the president's campaign."

The letter cites reports that Pence may have been aware of the contents of the president's July call in which Trump repeatedly pressed Zelensky to investigate a Ukrainian gas company whose board members had included Biden's son Hunter.

And the letter says Pence's absence from Zelensky's May inauguration may have been related to "efforts to put additional pressure on Ukraine to deliver on the president's demands."

House Democrats on Wednesday threatened to subpoena the White House if it doesn't turn over by Friday a host of documents that include any communication Pence's office had about the July call with Zelensky and information about Trump's decision not to send Pence to the inauguration. - USA Today