Washington (CNN) The FBI has issued "secret subpoenas" to a greater number of companies in its counterterrorism efforts than previously known, The New York Times reported Friday.

The Times said documents obtained by the Electronic Frontier Foundation through a Freedom of Information Act lawsuit and shared with the newspaper reveal "how far beyond Silicon Valley the practice extends -- encompassing scores of banks, credit agencies, cellphone carriers and even universities."

The documents, the newspaper said, show how often the FBI has used its power to collect information on individuals since 2001, when the Patriot Act expanded the agency's authority. The Times also said the documents "raise questions about the effectiveness of a 2015 law that was intended to increase transparency around" the subpoenas, known as national security letters. According to the Times, the letters don't require approval from a judge and are typically accompanied by an order preventing their recipients from discussing them to protect the government's counterterrorism operations.

The subpoenas were not included in the documents obtained through the lawsuit, but EFF was given redacted copies of notices to the companies that the order had been lifted, the newspaper said. The Times noted that the "so-called termination letters do not reveal the contents of the original national security letters, but indicate which entities received them."

The newspaper said that among the companies that received the letters were the credit agencies Equifax, Experian and TransUnion, as well as Bank of America, Western Union and other banking institutions. Some schools, including Kansas State University and the University of Alabama at Birmingham, also received the letters, the Times said, "probably because of their role in providing internet service."

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