A group of more than 30 congressional Democrats is demanding answers from the Transportation Security Administration about its treatment of transgender travelers.

The members of Congress raised questions about TSA screening procedures of transgender people in response to information obtained from the National Center for Transgender Equality’s 2015 U.S. Trans Survey. In the survey, which polled 28,000 transgender individuals, 53% of respondents indicated that they had encountered TSA agents when flying over the past year. Of that group, 43% reported having a negative experience.

Some transgender travelers reported that TSA agents instructed them to remove their clothing until they were nearly naked. Others complained of being groped, prodded, or publicly humiliated.

In response, U.S. Reps. Pramila Jayapal (D-Wash.) and Joe Kennedy III (D-Mass.), the chair of the Congressional Transgender Equality Task Force, led 30 of their colleagues in writing a letter to TSA Administrator David Pekoske asking for more information about these embarrassing encounters by the end of July.

In their letter, dated June 26, the members of Congress noted that the scanner technology used by transportation security officers requires officers to choose between two buttons on the machine based on their perception of a traveler’s gender identity. This can result in the machine identifying “anomalies” that flag the traveler for additional screening. And it puts them at higher risk of harassment or assault when they are outed as transgender to TSA agents or other travelers.

“We understand TSA has taken some steps to improve their processes and the experiences of all travelers,” the letter reads. “The TSA Cares initiative, for example, allows travelers to call with any questions they may have in advance of the TSA screening process. Additionally, we know that the agency has created videos to further educate and prepare travelers who will be passing through security, and that TSA has worked with stakeholders to improve their processes and training materials. However, more must be done to ensure our nation’s homeland security without compromising the civil rights of transgender processes.”

The members of Congress noted that TSA officials had testified before a House subcommittee about some of the practices utilized by TSA agents when dealing with transgender travelers, they also demanded additional information on the screening processes, the materials used to train security officers, and a timeline for when TSA will implement procedures to move beyond binary screenings.

The letter also asked whether there are less invasive measures, like explosives trace detection or canines that can be used in effectively screening transgender travelers, and what the process is of filing and resolving complaints lodged by travelers who wish to complain about TSA agents’ behavior toward them.

“We understand that homeland security is TSA’s top priority,” the lawmakers conclude. “However, we believe that meaningful efforts can be made to find solutions that are both safe and just. All travelers deserve to be treated respectfully — with their civil rights upheld — during their travels.”

See also: Congressional Transgender Equality Task Force demands meeting with Trump administration civil rights officials