WASHINGTON (AP) — Federal authorities investigating Rudy Giuliani are seeking information related to a former U.S. ambassador to Ukraine who was ousted from her job two years ago on orders of then-President Donald Trump, a lawyer for Giuliani said Friday.

Robert Costello confirmed via text message that a search warrant served this week on Giuliani made reference to Marie Yovanovitch, who as a central player in the first impeachment case against Trump detailed a smear campaign by Giuliani and other Trump allies that preceded her 2019 removal from the job. Costello said the warrant also referenced Ukraine's former top prosecutor Yuri Lutsenko, who met with Giuliani and was also part of efforts to remove Yovanovitch from her position.

The fact that the warrant makes mention of Yovanovitch, and that it seeks communication between Giuliani and several Ukrainians, suggests authorities are attempting to determine whether Giuliani's efforts to remove the ambassador were being done at the behest of Trump or of Ukrainians. That distinction matters because federal law requires anyone lobbying the U.S. on behalf of a foreign country or entity to register their work with the Justice Department.

Giuliani has denied any wrongdoing. The New York Times was first to report on the warrant's reference to Yovanovitch.

The May 2019 ouster of Yovanovitch was one of the pivotal episodes of the Trump impeachment case, coming just months before a phone call in which Trump urged his Ukrainian counterpart to investigate Democratic rival Joe Biden and his son, Hunter. Giuliani advanced those same efforts in his own discussions with Ukrainian officials, meeting with a Ukrainian lawmaker who released audio recordings during the 2020 presidential campaign in an effort to discredit Biden's candidacy.

Yovanovitch, a career diplomat who served for decades under both Republican and Democratic presidents and was first appointed by Ronald Reagan, testified in chilling detail during the impeachment trial about a “smear campaign” against her by Giuliani and others before her firing.

Yovanovitch also told House impeachment investigators that she'd been told by Ukrainian officials that Giuliani was in touch with Ukraine’s former top prosecutor Lutsenko “and that they had plans, and that they were going to, you know, do things, including to me.”

She said she was told Lutsenko “was looking to hurt me in the U.S.”

A lawyer for Yovanovitch declined to comment Friday.