House Democrats are looking into a second phone call made between President Donald Trump and Ukraine President Volodymyr Zelensky as part of an impeachment investigation that has upended the administration.

The call in question took place on April 21 of this year, shortly after Zelensky won election. There is no apparent White House read out of what was discussed between the two world leaders, but foreign press reports said it was congratulatory.

The call has been the subject of intense rumors and fascination for days, as more information has been made public about the pressure that Trump exerted on Zelensky to look into largely discredited allegations of corruption involving former Vice President Joe Biden and his son, Hunter.