New York ? A woman and her boyfriend were arrested Tuesday in the alleged beating death of her 4-year-old son, the latest in a recent series of child abuse fatalities that have rattled the city’s child welfare agency.

Alicia Smith, 26, faces a manslaughter charge in the death of Quachon Brown, police said. Her boyfriend, Jose Calderone, 18, was arrested on a second-degree murder charge.

Investigators believe Calderone physically abused the child, a police official said.

Quachon died Monday after police responding to a 911 call found him unconscious in the family’s filthy Bronx apartment.

Autopsy results were pending, but police said there was preliminary evidence that the child had a fractured skull, a damaged liver and atrophied leg muscles.

In November, Administration for Children’s Services caseworkers had visited the apartment where Quachon and several siblings lived and reported it “to be in order,” agency head John Mattingly said.