Sen. Bernard Sanders sent a letter to the director of the National Security Agency on Friday, demanding that he disclose whether the intelligence agency has spied on elected officials and members of Congress.

The Vermont independent’s letter to Keith B. Alexander comes after revelations over the past weeks and months that the American government may have spied on the phones and electronic devices of foreign leaders, as well as a district court ruling that challenged the constitutionality of the agency’s domestic surveillance programs.

“Has the NSA spied, or is the NSA currently spying, on members of Congress or other American elected officials? ‘Spying’ would include gathering metadata on calls made from official or personal phones, content from websites visited or emails sent, or collecting any other data from a third party not made available to the general public in the regular course of business,” Sanders wrote in the letter.

Sanders is one of several lawmakers who has introduced legislation that would limit the powers of the NSA and FBI to collect mass records from American citizens without suspicion or warrant.

Sanders’ full letter can be read here.