The American Civil Liberties Union (ACLU) called for greater transparency from the Federal Bureau of Investigation (FBI) about its aerial surveillance activities after obtaining documents through a Freedom of Information Act (FOIA) request detailing surveillance flights conducted during the Baltimore protests.

FBI and Baltimore police personnel ran 10 surveillance flights over Baltimore from April 29 through May 3, an ACLU blog said. At least half of the flights gathered video that was subsequently stored.

While the ACLU agreed aerial surveillance can be appropriate, the blog noted “it is essential that accurate information about such surveillance be available to the public, and that strict rules be in place to protect against unjustified mass surveillance or warrantless collection of private information.”

FBI Director James Comey recently told a House committee the agency used aircraft above Ferguson, Mo., and Baltimore but did not collect the contents of communication on the ground.