Caught in the Act

Lauren Conrad & Derek Hough Kiss on the Dance Floor

10/18/2011 at 06:00 AM EDT

Lauren Conrad and Derek Hough added fuel to the fire of dating rumors by partying together – very closely – in the back room at L.A.'s Trousdale Lounge. Though they were with friends – she had Lo Bosworth with her, and he was hanging out with Mark Ballas – they mostly spent time with each other. They even hit the dance floor, where Hough had his arm around Conrad's waist. "It was obvious there was a lot of chemistry between the two," an onlooker says. "She was very smitten." So smitten, in fact, that they shared some smooches. Says the onlooker: "Neither seemed embarrassed about kissing in public." – Jennifer Garcia

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