SEATTLE -- Investigators with Child Protective Services investigated complaints of abuse of the boy whose body was found Thursday three times in recent years, an agency representative told KIRO 7 Eyewitness News.

Sherry Hill of CPS told reporter Chris Legeros that of 10 complaints filed involving 29-year-old Shantina Smiley and her son, 8-year-old Azriel Carver, three were investigated.

Investigators looked into a June 2005 complaint that Azriel suffered serious physical abuse at the hands of Smiley's ex-boyfriend, and the man was arrested but never prosecuted, Hill said.

Investigators concluded a March 2007 complaint that Smiley abused her son was unfounded, Hill said.

In August 2007, CPS investigators found Smiley neglected the boy when he was unsupervised while she was passed-out drunk. Azriel was taken from his mother's care but returned to her after she got treatment, Hill said.

Hill said CPS is now conducting a review of the case to see whether the agency made mistakes.

Meanwhile, the Pierce County medical examiner's office on Friday said Azriel, whose body washed ashore on a Fox Island beach, drowned.

WATCH IT: Autopsy Concluded On Boy

The search continued for Smiley, who hasn't been seen since she was spotted with her son on Saturday night in Olympia.