House Oversight Committee Chairman Elijah Cummings said Tuesday that TSA told his committee it has dispatched nearly 200 screeners and supervisors and 172 air marshals to the border already and plans to send another 294.
"The administration's actions are not helping aviation security, they are harming it," the Maryland Democrat said during a hearing on TSA shortcomings.
Rep. Jim Jordan, R-Ohio, defended the Trump administration.
"Why are they sending TSA personnel to the border? Because there's a crisis," he said.
TSA has more than 60,000 employees.
TSA spokesman James Gregory told The Associated Press that employees who volunteer are sent to the border on 45-day rotations and can ask to stay longer.
Gregory said only 88 of the TSA employees currently at the border are airport screeners, although that number will fluctuate.
"The key is that we are managing voluntary deployments strategically to ensure no one airport or location is overly burdened," he said.
Also at the hearing, officials from the Homeland Security Department inspector general and the Government Accountability Office, an arm of Congress, said TSA has not fixed several weaknesses in airport security identified in several reports over a period of years. Many were discovered during covert tests, but the results were classified.
TSA Administrator David Pekoske said his agency has taken major steps to comply with recommendations on screener training and equipment and is committed to dealing with the others as soon as possible.