The Capitol Police have launched an investigation after new security measures at the Capitol stopped Rep. Andy Harris, R-Md., from carrying a gun onto the House floor, HuffPost is reporting.

Harris set off magnetometers outside the House chamber on Thursday. Metal detectors had been installed after the Jan. 6 riot at the Capitol.

An officer with a metal detector wand-scanned Harris and found the gun under the congressman’s suit coat, according to HuffPost. Police refused to allow Harris in and an officer motioned to a security agent that he had a gun.

HuffPost said it witnessed the interaction and confirmed with a Capitol official that Harris had been carrying a gun.

Harris left the scene after trying unsuccessfully to get another lawmaker to hold the firearm, HuffPost said. He later returned and went through the metal detector without setting it off and was permitted in.

The Washington Post, which said it confirmed the gun incident with a Hill staffer, said lawmakers are not permitted to bring guns into the House or Senate chambers.

Harris’ chief of staff Bryan Shuy told Fox Baltimore on Thursday night: “Because his and his family’s lives have been threatened by someone who has been released awaiting trial, for security reasons, the congressman never confirms whether he nor anyone else he’s with are carrying a firearm for self-defense.

“As a matter of public record, he has a Maryland Handgun Permit. And the congressman always complies with the House metal detectors and wanding. The congressman has never carried a firearm on the House floor.”