Efforts to regain customer trust at Chipotle Mexican Grill Inc. could suffer a setback as the restaurant chain put its top marketing executive on administrative leave after Manhattan prosecutors unveiled an indictment involving the executive and a cocaine drug ring.

While the indictment, made public on Thursday, has nothing to do with Chipotle itself, the involvement of an executive seen as the architect of its efforts to win back wary diners after an E.coli outbreak last fall could have a damping effect.

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