The scanners used to take passenger temperatures would likely be a mix of tripods that can scan multiple people at once and hand-held thermal devices, the administration official said. Passengers with a temperature reading of 100.4 degrees Fahrenheit or higher would be flagged. Officials haven’t yet decided whether the scanning will take place at the start of the security process or toward the end.

Democrats in Congress have for weeks raised questions about whether the administration has authority to conduct temperature checks without congressional approval.

“I cannot find any law that gives TSA the authority to perform temperature checks as reported,” said Rep. Bennie G. Thompson (D., Miss.), chairman of the House Committee on Homeland Security, in an emailed statement Friday.

The Trump administration “should not put these front-line workers in further danger in order to provide passengers a potential false sense of safety,” he said.