Salem Superintendent of Police Aswin Kotnis said the deceased were two 19-year-old second year BE students while the injured was a 20-year-old final year student.
The private bus was proceeding from Attur to Salem.
In December last, in a similar accident four students were crushed to death in Chennai prompting the Madras High Court to take a suo motu cognizance of the accident.
The court has proposed that if any student is found travelling on the footboard, the matter may be reported not only to the parent of the concerned student, but also to the Principal of the educational institution concerned.
"..And if he repeats the same thing for the second or third time, the school may take action for removal of such students, after notice to the parent," a Division Bench had said.
Hearing on the proceedings are continuing.