The mishap in Dharmapuri occured when a government bus on its way to Hogenakkal from Pennagaram went out of control and fell into a valley.
The bus fell when it took a sharp turn near a temple and fell into the valley some 50 feet below. The mishap in Padi occured when many two-wheeler riders and other motorists were waiting at a traffic signal.
Out of four dead, three died on the spot, another died at a hospital while the condition of one person is critical, police said.
They were hit by the speeding mini truck from behind."It is not known if the mishap occured due to brake failure or if the driver of the mini truck was drunk, probe is on," police said.