'High School Musical' star Zac Efron hasn't been seen much in recent months, but everyone assumed he was just working on his film career. And he was -- with a layover in rehab earlier this year. And the problem was apparently pretty severe.

On Tuesday afternoon, E! Online reported Zac did a stint in rehab this spring, with an insider saying he's now "healthy, happy and not drinking."

That was surprising enough, but a few hours later, TMZ's sources said Zac's drug of choice wasn't alcohol -- instead, it was cocaine and Ecstasy.

Apparently things got bad in April while Efron was filming a role in Seth Rogen's new movie 'Neighbors,' with an insider saying, "It was common knowledge [Zac] was struggling with cocaine."

Before going into rehab shortly thereafter, Zac also reportedly went on a "coke rager in a room at the SkyLofts at the MGM Grand in Vegas" that did about "$50k in damage."

His rep couldn't be reached for comment, but when Zac, 25, recently walked the red carpet at the Toronto International Film Festival, he looked great and reported he was doing "good, real good." Let's hope that's actually the case.

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