Unknown people on Wednesday pelted stones at polio vaccination team in Qazi Ahmed area of Nawabshah, injuring three workers. The stone-throwing incident took place at Hayat Marri Village in Nawabshah. According to reports, anti-polio workers, Khalid Soomro, Fauzia Mughal and Aftab Mughal, were also held hostage by miscreants. But they were timely freed by Qazi Ahmed police.