WASHINGTON (Reuters) - The FBI said on Thursday it executed more than 40 search warrants in the United States as part of its investigation into cyber attacks allegedly by a group called “Anonymous” that had backed WikiLeaks.

The cyber attacks, known as ‘distributed denial of service,’ were targeted against major U.S. companies and organizations and the search warrants coincided with the arrest of five people by British police in connection with the alleged attacks, the FBI said.

U.S. authorities have been looking into cyber-attacks on companies like Amazon and others targeted by hackers backing WikiLeaks after it published classified U.S. communications.