Ukraine has asked the FBI in the U.S. for help investigating a suspected cyberattack by Russian military hackers on Burisma, an energy company caught up in the impeachment of Donald Trump.

The Ukrainian interior ministry on Thursday also announced an investigation into the possible illegal surveillance of Marie Yovanovitch, formerly the American ambassador to Kiev, following the release of text messages this week by the U.S. Congress as part of the impeachment case.

The FBI said it had visited the home and business of Robert Hyde, a Republican congressional candidate in Connecticut who sent the text messages to Lev Parnas, an associate of Trump attorney Rudy Giuliani that suggested Hyde had Yovanovitch under surveillance. The FBI declined to give further details.