According to TMZ, Efron's drug problem "spiraled out of control" while on set of Seth Rogen's movie "Neighbors" back in April. Efron played the role of Teddy Sanders, a fraternity president.
The 25-year-old actor no-showed on several days of shooting. "It was common knowledge he was struggling with cocaine," said a source close to the film.
Other sources told TMZ that Efron also experimented with taking the drug Molly -- a form of Ecstasy.
The website reached out to Efron's rep, who said his camp won't make any comments on the matter.