Fifth Squad detectives are looking for an armed man who sexually assaulted a woman Sunday morning on a Fire Island beach, Suffolk County police said.

Officers responded to a call after witnesses in Cherry Grove reported a woman screaming for help at about 5:20 a.m., police said.

The woman told police a man armed with a silver handgun sexually assaulted and beat her on the ocean side of the community.

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The woman said the man was about 30 years old, 5-5, with a thin build, short black hair and a thin mustache.

Anyone with information can call Crime Stoppers, 800-220-8477, or the Fifth Squad, 631-854-8552. All calls will be kept confidential.