While the 27-year-old hotel heiress was walking the red carpet during a Hollywood event Thursday, the clamps holding the extensions were visible upon close inspection, the Daily Mail reported Friday.
The appearance of the extensions came after most fans of "The Simple Life" star assumed her shoulder-length hair was all natural, the British newspaper said.
Hilton, who accidentally revealed the fashion accessory at the nightclub Apple Lounge, has been an outspoken proponent for hair extensions in the past. The Mail said while serving as a spokeswoman for the hair extension company DreamCatchers, Hilton said great hair can serve as "the ultimate accessory."
"I think beautiful hair is the ultimate accessory," she said. "We use the best quality extensions and they always look fabulous."