FBI officials have been reviewing National Security Agency surveillance to ensure that messages collected as part of the PRISM email monitoring program did not belong to American citizens, according to a declassified report obtained by the New York Times. While exactly how the FBI has conducted this oversight remains unclear, the heavily redacted document appears to show that NSA surveillance is at least subject to review from outside the agency.

The report said the bureau in 2008 “assumed” the power to examine email accounts that the NSA wanted to track under PRISM, which collects the metadata from Yahoo and Google emails sent from outside the United States. In 2009, the FBI began to log its own copies of emails obtained without a warrant, before recommending more accounts and phone numbers for the NSA to track in 2012.

The Department of Justice report was finished in 2012 and made entirely classified at that time. The new information was included as part of a semi-redacted version issued to the Times in response to a Freedom of Information Act request. It’s the latest glimpse into the surveillance programs and judicial rulings that authorized them since details were first leaked to the press by former NSA contractor Edward Snowden in June 2013.

Those disclosures were followed by a wave of criticism arising from the fear that, with so much data being collected, it’s inevitable that innocent Americans would be swept up in the dragnet. Not so, according to FBI Inspector General Michael Horowitz, who wrote in the report that the FBI was “doing a good job in making sure that the email accounts targeted for warrantless collection belonged to non-citizens abroad.”

The Times said it got hold of the report late Friday.