“Mr. Manafort has consistently cooperated with law enforcement and other serious inquiries and did so on this occasion as well,” said Jason Maloni, the spokesman. News of the search warrant was first reported on Wednesday by The Washington Post.

The warrant is the latest troubling development for Mr. Manafort, a longtime Republican operative who has spent the last couple of decades working abroad as a consultant to foreign governments.

Mr. Manafort was hired by Mr. Trump’s campaign in early 2016 as it prepared for a potential delegate fight at the Republican National Convention. In June, he was named campaign chairman but resigned just two months later amid reports that he had received millions of dollars in off-the-book payments for his consulting work in Ukraine.

Since then, Mr. Manafort has been battered by a series of disclosures that have raised questions about his business dealings, as well as his participation in the June 2016 meeting between Trump campaign officials and Russians claiming to have damaging information on Hillary Clinton.

The search was carried out at Mr. Manafort’s home in Alexandria, Va., shortly after he met with investigators for the Senate Intelligence Committee on July 25. In that meeting, Mr. Manafort answered questions and provided investigators with notes from the June 2016 meeting with the Russians.

“A search warrant is very bracing for the person who is being searched,” said Jack Sharman, the former special counsel to the House Banking Committee during its Whitewater investigation of President Bill Clinton in the 1990s. “It’s very invasive and sends a loud statement from the prosecutors to the person that there should be no doubts about the seriousness of the investigation.”

“The government will be investigating something like public corruption, and it knows that you know something about it,” said Mr. Sharman, now a white-collar criminal defense lawyer at Lightfoot, Franklin & White. “The government will then come after you on something unrelated, where you have criminal exposure, in the hopes that you will cooperate on their public corruption investigation.”