A Port Jefferson man was arrested early Saturday for violating the social host law after police discovered about 400 people partying at his house — including underage revelers, officials said.

Police responded to the house on Crystal Brook Hollow Road at about 12:45 a.m. after receiving a call and came upon the party “where underage drinking was observed,” Suffolk County Police said in a news release.

Michael Malguarnera, 30, was charged with violating the social host law and was taken to the Sixth Precinct where he was released on bail, police said.

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He was scheduled for arraignment at First District Court in Central Islip on Aug. 18, according to police.

Attorney information for Malguarnera was not immediately available.