Friends' fears for Zac after bustup in shady part of town

Zac Efron's friends are "worried sick" he has fallen off the wagon.

The 'High School Musical' actor ran into trouble in an area of downtown Los Angeles notorious for being awash with drug dealers and dangerous at night on Sunday, and pals claim they don't believe he had driven there in search of sushi - as he told police - and fear he is back on drugs.