Paul Manafort Home Searched by FBI

In this photo taken July 17, 2016 photo, Paul Manafort talks to reporters on the floor of the Republican National Convention at Quicken Loans Arena in Cleveland. Manafort says he’s registering with the Justice Department as a foreign agent. Michael Flynn already did. And in both cases the filings by associates of President Donald Trump will come after the fact and accompanied by the admission that they violated federal law. (AP Photo/Matt Rourke)

Investigators for the special counsel leading the Russia inquiry executed a search warrant late last month at the Northern Virginia home of President Trump’s former campaign manager, Paul J. Manafort, for tax documents and foreign banking records, according to a person familiar with the matter. The search is a sign that the investigation into Mr. Manafort has broadened, and is the most significant public step investigators have taken since the special counsel, Robert S. Mueller III, was appointed in May.

Investigators are expected to deploy a wide array of similar measures, including interviews and subpoenas, in the coming months as they move forward with the intensifying inquiry. It was not clear why Mr. Mueller did not simply ask Mr. Manafort’s lawyers for the documents. Executing a search warrant is considered among the most aggressive steps used by authorities, who must first demonstrate they have probable cause to believe they will find evidence that a crime occurred. The searches also often become public. Legal experts said that Mr. Mueller might be trying to send a message to Mr. Manafort about the severity of the investigation, and to pressure him into cooperating.

A spokesman for Mr. Mueller declined to comment. The person familiar with the inquiry spoke on the condition of anonymity because he did not want to be identified discussing a continuing federal investigation.