Released: July 16Distributor: HBO Films/Fine Line Features With its low-key naturalism and social conscience on its sleeve, “Maria Full of Grace” could have been seen as merely a well-meant investigation of yet another of life’s unbearable sadnesses, Latin American- style. But since its world premiere at the Sundance Film Festival, where it won the dramatic audience award in January, this film has been hailed by critics as a true event, noted in particular for its script, director and lead actress. What’s remarkable is that “Maria” is the feature debut of both its 23-year-old Colombian star, Catalina Sandino Moreno, and its California-raised writer-director Joshua Marston. With dialogue in Spanish, the modestly budgeted pic was produced by an American, Paul Mezey, and funded by a U.S. company. This, in addition to the fact that the filmmaker is American, means that the film does not qualify for Oscar’s foreign lingo category. Despite that, “Maria” could well score in other kudo slots. Sandino plays a willful 17-year-old Colombian girl, who, when she finds out she’s pregnant by her indifferent boyfriend, decides to leave her oppressive factory job in favor of a shot at something bigger — a drug mule gig to the U.S. that pays $5,000, if successful. There is never a clear indication that this is absolutely her last resort. But the detailed portrayal of what it really entails — including swallowing 62 latex bullets full of cocaine — is as harrowing. Ultimately, it’s Marston’s improvised naturalism that gives the film power, and the quiet forbearance of his lead actress, whose face in repose recalls Catholic statuary, that makes it haunting. New York Times reviewer Stephen Holden wrote the pic “sustains a documentary authenticity that is as astonishing as it is offhand. Even when you’re on the edge of your seat, it never sacrifices a calm, clear-sighted humanity for the sake of melodrama or cheap moralizing.” A summer release, “Maria” has taken in $6.3 million at the U.S. box office, an unusually high tally for arthouse fare, and it’s done particularly well on the festival trail. Among its prizes after Sundance, it won best first feature and a Silver Bear for Moreno in Berlin. In a year in which films of political and social conscience are regaining favor, this outsider entry might prove more than a casual contender.