NEWARK, N.J. (1010 WINS/ AP)  -- An infestation of fleas and mice may be to blame for the allergic reactions that sent dozens of residents of a Newark apartment building to the hospital on Tuesday, officials said.

A city spokeswoman said Tuesday night that there had been past complaints about pests in the building, but that the exact cause for the residents' ailments has not yet been determined. It was not clear if there had been an effort to exterminate the pests prior to the residents becoming ill.

Esmeralda Diaz Cameron, spokeswoman for Mayor Cory Booker, said crews were working Tuesday night to fumigate the building and do a thorough cleanup. Thirty-eight families who lived in the building were temporarily relocated to a nearby YMCA building, she said.

Booker stressed that the problem was confined to the single building and posed no threat to anyone else in the neighborhood. He went door-to-door to reassure nearby residents.

``We are taking every measure to identify and eradicate the problem. This is an isolated situation, and over the next 24 hours we will continue to investigate,'' Booker said.

Earlier in the day, environmental officials were unable to find any hazardous material or evidence of chemicals at the apartment building.

Fire department spokesman John Brown said the residents who were hospitalized were treated with Benadryl and steroids and were likely to be released.

Residents complained of swollen eyes, rashes and skin irritation, Cameron said.