Federal prosecutors are now looking into whether Rudy Giuliani, President Trump's personal lawyer, failed to register as a foreign agent and violated campaign finance laws, three U.S. officials told Bloomberg News.

The U.S. attorney's office in Manhattan reportedly began investigating Giuliani and his dealings in Ukraine after they launched a probe into two of his business associates, Lev Parnas and Igor Fruman. Last month, Parnas and Fruman were arrested and charged with illegally funneling foreign money into U.S. campaigns. Parnas and Fruman worked with Giuliani in Ukraine, attempting to dig up dirt on Democrats.

Several top State Department officials have testified during the House impeachment inquiry that earlier this year, Giuliani was running a shadow campaign when it came to Ukraine. They said he spread rumors to force out then-Ambassador to Ukraine Marie Yovanovitch, and was searching for any information that could damage Trump's potential political rivals.

Based on what they know about the matter, one U.S. official told Bloomberg News it is possible prosecutors could charge Giuliani with violating laws against bribing foreign officials or conspiracy. "I would not be surprised if he gets indicted," former federal prosecutor Mimi Rocah told Bloomberg News. "It's clear Giuliani is up to his ears in shady stuff and there's tons of smoke." Catherine Garcia