The accident took place when the driver of the mini truck fell asleep while driving, they said.
The deceased have been identified as Gurpreet Singh, Harjit Singh and Pappu, all teenagers and residents of village Shehbaazpur near Raikot in Ludhiana district.
While 25 of injured were admitted in Ropar and Chamkaur Sahib hospitals, two others have been referred to PGIMER Chandigarh.