KYIV, Ukraine — Police in Ukraine are investigating whether the U.S. ambassador came under illegal surveillance by an unknown party before the Trump administration recalled her from Kyiv, Ukrainian authorities said Thursday.

The announcement came two days after Democratic lawmakers in the United States released documents and text messages that showed an associate of President Donald Trump’s personal lawyer communicating with Rudy Giuliani about Ambassador Marie Yovanovitch’s removal.

In announcing the investigation, the Ukrainian Interior Ministry said the country’s police “are not interfering in the internal political affairs of the United States” by conducting the probe.

The ambassador’s firing last spring was at the center of the inquiry launched by House Democrats that led to the president’s impeachment.  But it was the trove of newly released information from smartphones belonging to Giuliani associate Lev Parnas that prompted the Ukrainian police investigation.

In text messages to Parnas, Republican congressional candidate Robert F. Hyde gave updates on Yovanovitch’s location and cellphone use. Hyde suggested in a tweet this week that the messages that made it sound like the ambassador was being watched were a joke.

Parnas has said Hyde’s texts shouldn’t be taken seriously, but officials in Ukraine indicated they have a legal obligation to determine if the former ambassador was subject to surveillance by an unknown party.