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An early morning tweet from Katy Perry has added to speculation of a feud between her and Taylor Swift.

The "Dark Horse" singer made a reference to the film "Mean Girls" in a tweet to her 56.7 million followers.

"Watch out for the Regina George in sheep's clothing…" Perry, 29, wrote referring to the Rachel McAdams character who faced off against Lindsay Lohan in the 2004 hit comedy.

The jab appears to refer to Swift's recent interview with Rolling Stone, in which she opened up about a fellow unnamed artist with whom she is "straight-up enemies."

"She would come up to me at awards shows and say something and walk away, and I would think, 'Are we friends, or did she just give me the harshest insult of my life?'" Swift told the magazine. "(Then last year) she did something so horrible. I was like, 'Oh, we're just straight-up enemies.' And it wasn't even about a guy!"

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Instead, "it had to do with business," Swift said. "She basically tried to sabotage an entire arena tour. She tried to hire a bunch of people out from under me. And I'm surprisingly non-confrontational-you would not believe how much I hate conflict. So now I have to avoid her. It's awkward, and I don't like it."

Like previous Swift songs, the singer channeled her feelings into "Bad Blood," a track on her latest album, "1989."

"I'm not the female police - but it broke my heart," Swift told the Rolling Stone. "Because I have such a high priority on girls sticking together."

Swift is known for her close friendships with her famous BFFs, including Selena Gomez, Lena Dunham, Lorde, Emma Stone, Sarah Hyland and Dianna Agron.