A 2021 federal raid on Rudy Giuliani’s home and office was spurred by suspicions that the former New York City mayor had sought the removal of the U.S. ambassador to Ukraine partly because of the prospect of a financial reward from a Ukrainian official, according to documents made public Tuesday.

The documents provide new detail on the since-concluded investigation into Giuliani’s involvement with Ukrainian figures in the run up to the 2020 presidential election. Giuliani, a longtime ally of former President Donald Trump, was not charged with a crime as a result of the inquiry.

In a search warrant application, federal agents seeking to seize Giuliani’s cell phones, laptop and other electronic devices raised the possibility that he and three other people could be charged with acting as unregistered foreign agents.

The documents, unsealed at the request of The New York Times and dating to the weeks before the raids, confirmed past news reports that federal prosecutors in Manhattan were examining whether Giuliani had gotten anything of value from Ukrainian figures in return for lobbying the Trump administration to fire then-U.S. Ambassador to Ukraine Marie Yovanovitch.