Mario Lopez and girlfriend Karina Smirnoff, his partner on last season's Dancing with the Stars, recently took their relationship to the next level: They're cohabiting.

"They recently moved in together," a source close to the couple tells PEOPLE. "It was a big step to take, especially for Mario, but they both think this could be it. Things are going really well right and they're loving being together all the time."

The 33-year-old Lopez and the Ukrainian-born Smirnoff have always been coy about their romance since coming in second on the ABC reality hit in November, but were spotted vacationing together in Mexico later that month.

Lopez, who will co-host the Miss Universe 2007 pageant on NBC live from Mexico City on May 28, told PEOPLE at the time that he and Smirnoff had "a very special relationship" and said: "We're great friends and very supportive of each other."

Reps for both had no comment.



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