The mishap occurred at around 3 AM this morning near Manchirevula village of neighbouring Ranga Reddy district when a speeding lorry rammed into the ambulance from the rear side, a police officer said.
The deceased were identified as Deepika (28), her husband Viswanath (32) and mother Bharathi (50). Deepika's father Prabhakar escaped with injuries, he said.
The family had gone to Mumbai for treatment of Deepika for some ailment and was on way to their native place in West Godavari district of Andhra Pradesh, the officer said.