The Pentagon is carrying out warrantless surveillance of Americans, according to a new letter written by Senator Ron Wyden and obtained by Motherboard.

Senator Wyden’s office asked the Department of Defense (DoD), which includes various military and intelligence agencies such as the National Security Agency (NSA) and the Defense Intelligence Agency (DIA), for detailed information about its data purchasing practices after Motherboard revealed special forces were buying location data. The responses also touched on military or intelligence use of internet browsing and other types of data, and prompted Wyden to demand more answers specifically about warrantless spying on American citizens.

Some of the answers the DoD provided were given in a form that means Wyden’s office cannot legally publish specifics on the surveillance; one answer in particular was classified. In the letter Wyden is pushing the DoD to release the information to the public. A Wyden aide told Motherboard that the Senator is unable to make the information public at this time, but believes it would meaningfully inform the debate around how the DoD is interpreting the law and its purchases of data.

“I write to urge you to release to the public information about the Department of Defense’s (DoD) warrantless surveillance of Americans,” the letter, addressed to Secretary of Defense Lloyd J. Austin III, reads.

Wyden and his staff with appropriate security clearances are able to review classified responses, a Wyden aide told Motherboard. Wyden’s office declined to provide Motherboard with specifics about the classified answer. But a Wyden aide said that the question related to the DoD buying internet metadata.