Police have launched an investigation into Amanda Bynes' allegations she was mistreated by one of the cops who arrested her in New York on Thursday (23May13).

The Hairspray star was taken into custody and later charged on suspicion of marijuana possession, attempted tampering with physical evidence and reckless endangerment, after allegedly throwing a bong out of the window of her 36th-storey apartment in Manhattan.

She later took to Twitter.com to rant about her arrest, and Bynes claims she was treated badly by one of the police officers.

In an extended post on the microblogging website, the troubled star writes, "Don't believe the reports about me being arrested. It's all lies. I was sexually harassed by one of the cops the night before last which is who then arrested me. He lied and said I threw a bong out the window when I opened the window for fresh air. Hilarious. He slapped my vagina. Sexual harassment. Big deal. I then called the cops on him. He handcuffed me, which I resisted, quite unlike any of the reports stated. Then I was sent to a mental hospital. Offensive. I kept asking for my lawyer but they wouldn't let me. The cops were creepy. The cop sexually harassed me, they found no pot on me or bong outside my window."

A spokesperson for the New York Police Department (NYPD) has now confirmed they are investigating Bynes' allegations, telling The Hollywood Reporter that members of the NYPD's Internal Affairs Bureau are probing the claim.

Bynes, who was taken to Roosevelt Hospital for a psychiatric evaluation after her arrest, was released on her own recognisance after appearing in court in Manhattan on Friday morning (24May13).