Infant-sized arm found by sewage plant worker

State officials are investigating the discovery of what appears to be part of an infant's arm, found floating by a stunned worker yesterday in waste at the Deer Island Sewage Treatment Plant on Boston Harbor, according to the Suffolk district attorney's office.

An employee discovered the limb in an area of the plant where solid materials are separated from liquid flow, David Procopio, a spokesman for the Suffolk District Attorney, said in a statement.

The arm was taken to the Office of the Chief Medical Examiner in Boston to determine the age of the child and time of death, Procopio said. No other detail of the limb was provided, and no other human parts were found at the plant yesterday, he said.

The employee who found the limb was shocked, said Ria Convery, a spokeswoman for the Massachusetts Water Resources Authority, which overseas the plant.

''Our staff found something that appeared to be the limb or remains of a limb of a small child," Convery said in a telephone interview last night. ''It was identified as infant-like in size."

The arm could have flowed in from many locations, Convery said.

''It is quite a mystery. We are not sure how it ended up here," she said.

The incident is being investigated by State Police, who determined that the limb was found in waste originating from Boston or the area immediately north of the city, Procopio said. Investigators are contacting local police departments, including those in Revere, Winthrop, Chelsea, East Boston, and Everett, for reports of missing infants, Procopio said.

The plant, just south of Winthrop, processes human waste and household, business, and industrial pollutants from waste water pumped in through pipes from homes and businesses in 43 communities, Convery said. Waste water from MWRA customer communities arrives at the plant through four underground tunnels, according to the plant website.

Officials said they could not recall the last time a body part was found at the plant.