The deceased were identified as Ghulam Hussain, an employee of Hesco, his mother Zainab Bibi and wife Maqbool.
His sister suffered injuries.
The injured were lying on the road in critical condition for a considerable time and their shifting to hospital was delayed. They were residents of Gulshan-i-Zeal Pak.
The bodies were sent to Sadiq Shah village, Khairpur district.