The mishap took place after the truck hit the median, swerved to the opposite lane on the highway here at Chinnar and rammed into the Hosur-bound bus from Krishnagiri.
"Seven persons died on the spot, including a woman and the cleaner of the truck. The injured are being treated at a hospital," Shoolagiri Police Inspector C Sampath said.
"Thirty two people were injured and some of them are serious," he said, adding, "a case is being registered and a probe is on."
The incident led to traffic snarl on the highway to Hosur for sometime.