Three persons were killed and nine others injured when an old building collapsed at Zakir Hussain slum area here, with several people feared trapped inside, police said today. The four-storeyed building collapsed at about 10.30 PM last night, a police official said. As fire brigade personnel and locals joined hands for the rescue operation, the authorities sought help from the Army in the wee hours of the morning. So far, three bodies have been recovered. Nine injured people were rescued and admitted to hospital, the official said adding that rescue work was continuing as several people were feared trapped inside.