Over 40 labourers were returning from work to Gurazala when the vehicle lost control and overturned near a lake in Jangameswaram near here.
Four persons were killed on the spot, while 20 others sustained injuries, they said.
Two of the injured were said to be in a critical condition, according to local MLA Yerapatineni Srinivasa Rao.
The two were rushed to Government General Hospital in district headquarters Guntur for better treatment while the other injured were being treated in a local hospital at Gurazala.
Rao announced an ex-gratia of Rs 25,000 each to the kin of those killed.