Investigators searched the Manhattan apartment and office of former New York City mayor Rudy Giuliani early Wednesday morning as part of a federal probe into his business dealings with Ukraine. In a related development, authorities also raided the home of Washington attorney Victoria Toensing, a former federal prosecutor and well-known associate Giuliani’s.

The Department of Justice has been trying to determine whether Giuliani, the personal lawyer for former president Donald Trump, illegally lobbied the Trump administration in 2019 on behalf of Ukrainian officials and oligarchs for, among other things, pushing to have the American ambassador to Ukraine removed.

The alleged activity was done as a favor in return for helping Giuliani in his search for compromising information to use against then-President Trump’s political rivals. That would include President Joe Biden and his son Hunter, who was once on the board of a Ukrainian company.

Giuliani’s attorney, Robert Costello, took a page from his client’s playbook during his many defenses of former president Trump and went on the offensive to criticize authorities. “What they did today was legal thuggery,” Costello said. “Why would you do this to anyone, let alone someone who was the associate attorney general, United States attorney, the mayor of New York City and the personal lawyer to the 45th president of the United States.”

According to what sources told the New York Times, investigators seized one of Giuliani’s electronic devices. The US Attorney’s office in Manhattan and the F.B.I. had reportedly been trying for months to obtain a search warrant for Mr. Giuliani’s phones, but higher-ups in the DOJ under former Attorney General Bill Barr slow-walked and even tried to block the process.

With Merrick Garland now overseeing the Justice Department, those obstacles are now removed.

The warrant is not proof of any wrongdoing by Giuliani, but it indicates the investigation is gathering momentum. Investigators need to persuade a judge they have sufficient reason to believe that a crime was committed to and that a search would turn up crucial evidence, to obtain a warrant.

More than that, prosecutors showing up for pre-dawn searches at the homes of a former lawyer, someone who represents a former U.S. President, is an extraordinary step and signals the probe into Giuliani is ramping up. Former U.S. Attorney for the Southern District of NY Preet Bharara certainly thinks so.

Prosecutors charged two men with known ties to Giuliani, Lev Parnas and Igor Fruman, with unrelated crimes in late 2019. They’re due to stand trial in October.

Neither the F.B.I. or the U.S. attorney’s office commented on Wednesday’s search at Giuliani’s Upper East Side apartment.