Airport security agents got a surprise on Tuesday when a woman in a wheelchair approached a checkpoint in Oklahoma City, took off her trench coat and was wearing only a black lace bra and panties. (YouTube)

OKLAHOMA CITY - Airport security agents got a surprise on Tuesday when a woman in a wheelchair approached a checkpoint in Oklahoma City, took off her trench coat and was wearing only a black lace bra and panties.

Airport and security officials said that police were called over, questioned the woman, Tammy Banovac, and allowed her to proceed to security.

She was given an “enhanced” pat down because she was in a wheelchair. During screening of her carry-on and laptop an alarm for nitrates was triggered, the Transportation Safety Administration said in a statement Wednesday.

The TSA said she was not allowed to proceed to her Southwest Airlines flight to Phoenix.

Authorities said nitrates could legitimately be present in medication, or if someone was hunting recently and there were traces of nitrates from the bullets.

A video of the underwear-clad Banovac, wearing a pearl necklace and holding a small white dog in her lap, was shot by a passerby and posted on YouTube.

Officials said they had no idea why Banovac acted the way she did, or if she was attempting to protest airport security.

TSA has come under attack in recent weeks for enhanced methods of patting down passengers, but Oklahoma City Airport spokeswoman Karen Carney said TSA acted appropriately.

“TSA did everything they should have done,” said Carney.

Banovac returned to the airport Wednesday morning, again clad in her underwear, and cleared security without incident.

“Once she went through the checkpoint, she put slacks and a top on,” Carney said.

Banovac could not be reached for comment.