Getting cozy at Comic-Con! Before Orlando Bloom made headlines for his confrontation with Justin Bieber, he had a close encounter with Nina Dobrev, who sunk her teeth into the actor at Comic-Con in San Diego, Calif., last Friday, July 25.

Eyewitnesses tell Us Weekly that the steamy PDA between the Vampire Diaries actress, 25, and Bloom, 37, took place at Zachary Levi's Nerd HQ bash sponsored by Patron XO Cafe.

According to one observer, the stars "were making out for 20 minutes." Insiders said neither could peel their eyes—or hands—off each other at the bash.

"They grinded on the dance floor," a second eyewitness says of the pair.

Their familiarity with each other is nothing new. Dobrev and Bloom first met through a mutual contact—their manager Scott Wexler—and were even spotted holding hands in January.

"Nina has known Orlando for a few years now," a source told Us. "She's been out with him in social settings with mutual friends. She's always thought he was an attractive man."

The Hobbit actor split from his wife Miranda Kerr in October after three years of marriage, while Dobrev went through two breakups last year. The first was with her Vampire Diaries costar Ian Somerhalder in May, and the second with Dancing With the Stars pro Derek Hough.

For now, it appears that neither Dobrev nor Bloom are looking for anything too heavy. A source close to the actress tells Us, "She's single and having fun!"

For more on their steamy makeout—plus details on Kendra Wilkinson's night out without Hank Baskett, Sandra Bullock's 50th birthday party, and Khloe Kardashian's reckless rebound—watch this week's Hot Stuff video featuring Us Weekly Entertainment Director Ian Drew and RuPaul's Drag Race season six runner-up Courtney Act.