Katie Holmes, Luke Kirby More Than Co-Stars?

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Katie Holmes certainly wouldn't be the first to find romance on set.

Nearly a year after divorcing Tom Cruise, the 34-year-old actress was seen out with her "Mania Days" co-star Luke Kirby Tuesday night after a day of filming in New York City.

They were seen strolling together, with grins on their faces, prompting some reports to suggest life might be imitating art.

Reps for both stars did not immediately respond to ABCNews.com's request for comment.

A source told ABCNews.com, "They're starring in a movie together, they're having a wonderful time working together and they are just friends."

Holmes and Kirby play a manic-depressive couple who meet at a psychiatric hospital and fall in love in the Spike Lee-produced romantic drama. They were seen earlier Tuesday laughing and holding hands, while getting soaked in a park fountain during one romantic scene.

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The co-stars' chemistry was also on display last week while shooting scenes on a city sidewalk, laughing and holding hands.

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Canadian actor Kirby, 34, most recently played a romantic lead opposite Michelle Williams in "Take This Waltz." He can also be seen on the Sundance Channel show "Rectify."

Holmes, the mother of 6-year-old Suri Cruise, has remained single since her divorce from Cruise in August.

She told Allure magazine in March that although there was no man in her life, she can envision a time when she might want to expand her family.

"I don't know," she said. "I'm open to it."