A sensitive conference call between FBI and British police's cybercrime investigators was recorded by the very people they were trying to catch, officials and hackers said Friday.

Hacking collective Anonymous published a roughly 15-minute-long recording of a conference call apparently devoted to tracking and prosecuting members of the loosely-knit group.

The FBI said the information "was intended for law enforcement officers only and was illegally obtained."

"A criminal investigation is under way to identify and hold accountable those responsible," the bureau said in a statement.

It's not clear how the hackers got their hands on the recording, which appears to have been edited to bleep out the names of some of the suspects being discussed.

"The FBI might be curious how we're able to continuously read their internal comms for some time now," the group gloated in a message posted to Twitter.

Amid the material published by Anonymous was a message purportedly sent by an FBI agent to international law enforcement agencies. It invites his foreign counterparts to join the call to "discuss the ongoing investigations related to Anonymous ... and other associated splinter groups." The email contained a phone number and password for accessing the call.

The email is addressed to officials in the U.K., Ireland, the Netherlands, Sweden and France, but only American and British officials can be heard on the recording.

Graham Cluley, an expert with data security company Sophos, said that hackers had been able to eavesdrop on the call because they had compromised an investigator's emails.

"No doubt the police authorities will be appalled to realize that the very people that they are trying to apprehend, could have been tuning in to their internal conversations," he wrote in a blog post.

An email to the FBI agent who sent the email was not immediately returned, while one of the British investigators on the call referred questions to Scotland Yard's press office.

The press office said it was still working on a statement.

The recorded discussion itself appears sensitive. Those on the call talk about what legal strategy to pursue in the cases of Ryan Cleary and Jake Davis _ two British suspects linked to Anonymous _ and discuss details of the evidence gathered against other suspects.

Karen Todner, a lawyer for Cleary, said that the recording could be "incredibly sensitive" and warned that such data breaches had the potential to derail the police's work.

"If they haven't secured their email it could potentially prejudice the investigation," she told The Associated Press.

Anonymous is an amorphous collection of Internet enthusiasts, pranksters and activists whose targets have included the Church of Scientology, the music industry, and financial companies such as Visa and MasterCard.

Following a spate of arrests across the world, the group and its various offshoots have focused their attention on law enforcement agencies in general and the FBI in particular.

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Raphael Satter can be reached at: http://twitter.com/razhael