AUBURN — A 30-year-old Lewiston man has pleaded not guilty to charges of murdering a 22-year-old woman who advertised escort services on the Internet.

Buddy Robinson was arraigned today in Androscoggin County Superior Court in Auburn.

Robinson was charged last month in the death of Christiana Fesmire, who was last seen in July and whose body has not been found. In a police affidavit, investigators said Robinson drowned Fesmire in the bathtub of her apartment, which was in the same building where Robinson lived, but police do not indicate a motive.

An affidavit said Fesmire was part of an online prostitution ring led by Robinson’s sister, who told police that her brother confessed to the killing.