Update: Paul was rebooked on another flight, according to the TSA, and “was rescreened without incident.”

Original post: U.S. Sen. Rand Paul (R-Ky.) refused a pat-down after running afoul with federal security officials at a Nashville airport on Monday and was not allowed to board a flight, according to his father and federal officials.

His father, GOP presidential candidate and U.S. Rep. Ron Paul (R-Texas), sent a message via Twitter that said “My son @SenRandPaul being detained by TSA for refusing full body pat-down after anomaly in body scanner in Nashville.”

Federal officials denied that the senator had been detained. They said something he was carrying set off an alarm when he passed through a millimeter wave scanner at the airport security checkpoint. The undetermined item showed up as a yellow box on the cookie-cutter image that the scanner shows on a security monitor.

When that happens, Transportation Security Administration rules require that the passenger submit to a pat down. Federal officials said the senator declined, was not permitted to board the flight and was escorted from the area. But he was not detained, they said.

“When an irregularity is found during the TSA screening process, it must be resolved prior to allowing a passenger to proceed to the secure area of the airport,” said Greg Soule, spokesman for the TSA. “Passengers who refuse to complete the screening process cannot be granted access to the secure area in order to ensure the safety of others traveling.”

The senator and his father have been among the most ardent critics of the federal air security agency.

Rand Paul was headed to Washington to speak at the March for Life events marking the anniversary of the Supreme Court’s Roe v. Wade decision, according to a post on his Twitter account.