The ill-fated bus, carrying 22 labourers, was headed to Bangalore when it hit the hill at around 1 AM at the Guvvalachervu ghat in the district, they said.
While four persons died on the spot, two succumbed later at a hospital in Kadapa.
Three of the deceased hailed from Chhattisgarh and the others were from Andhra Pradesh.
The deceased have been identified as - Lodi Kondaiah (22), Gollavari Buddi (17), Karna Raju (20), Bandaru Adem (20), Gollari Babu Rao (22) and Gollari Nandin (35).
Ramapuram police have registered a case in this regard.
The injured persons were shifted to Rajiv Gandhi Institute of Medical Sciences at Kadapa.