A new transparency report Google released on Wednesday disclosed a previously secret FBI inquiry for user data.

Google wrote in its biannual report that an FBI gag restriction on the subpoena or national security letter issued in the second half of 2015 had been lifted.

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The Intercept first reported on the subpoena mentioned in Google’s transparency report.

Law enforcement officials' power to use national security letters was greatly extended after the passage of the Patriot Act. The letters do not require a judge’s approval like warrants, and those who receive the letters are barred from publicly talking about them.

The FBI and Department of Justice must periodically review national security letters to assess if the gag restrictions are still necessary, according to the Intercept’s report. The restriction is supposed to be lifted after either three years or when the investigation has concluded depending on which comes first.

Google didn’t release the actual letter as other companies previously have, though it intends to at an unspecified point in the future.

Though Google only noted receiving one national security letter from the latter half of 2015, the company has received more in the past and fought against them.