A Japanese zoo is conducting a probe after accidentally killing 31 out of 40 squirrels with anti-parasitic medicine and insecticide. The Inokashira Park Zoo injected the squirrels with the medicine and sprayed insecticide on their nest boxes as a sanitary precaution. The zoo admitted the possibility of drug-induced poisoning and is currently investigating the cause of the deaths. Pathological examination of the corpses is underway. The facility has been cleaned and deemed safe, and the surviving squirrels are back on display.