The driver of the bus lost control over the vehicle when he applied brakes to avoid hitting a mentally challenged beggar walking in the middle of the road around 7.30 AM, police said.
The bus was coming to the city from Erode.
The deceased have been identified as Karthik (18), Yamuna (41), Parthasarathy (32) and Darsh Agarwal (6), while the identity of three others is yet to be ascertained.
Tirupur District Collector, Govindarajan and Superintendent of Police, Amith Kumar Singh visited the area, to oversee the rescue operations.
Preliminary investigation revealed that the bus was over-speeding and overloaded, police said, adding, the driver is being questioned.