(CNN) -- The loose organization of hackers known as Anonymous released Friday a recording of a telephone call between the FBI and Scotland Yard that it said it recorded surreptitiously.
The group posted the 16-minute conference call on one of its websites.
The FBI and Scotland Yard acknowledged that the released recording was intended to be a private conversation, but blamed no particular group.
A U.S. law enforcement source said the conversation was recorded after an e-mail that circulated Jan. 13 to the conference call participants was intercepted when one of those participants forwarded it to a personal e-mail account. "It's not that sophisticated," the source said. "It's like vandalism."
"The information was intended for law enforcement officers only and was illegally obtained," the FBI said in a statement. "A criminal investigation is under way to identify and hold accountable those responsible."
In the recording, law enforcement officials can be heard discussing advances in investigations into hackers. Some of the names of the hackers are bleeped out in the recording, while others are not.
The law enforcement source told CNN that the call took place on January 17, and concerned an investigation by British authorities into the LulzSec hacker group. The official said that no FBI computer systems were hacked.
The agency has been investigating Anonymous for more than a year.
Also on Friday, Anonymous announced that it planned to release e-mails related to the 2005 deaths of 24 unarmed Iraqi civilians during a U.S. military raid in Haditha.
Anonymous posted online that it has hacked into Puckett & Faraj, a law firm representing one of the soldiers involved in the Haditha incident. The hackers say they have stolen 2.6 gigabytes of information from the firm including "detailed records, transcripts, testimony, trial evidence, and legal defense donation records," the online announcement said.
The law firm did not immediately respond to a request for comment.
CNN's Carol Cratty, Dugald McConnell and Ashley Fantz contributed to this report.