The victims have been identifies as three males and two females; residents of Periyakulam area.
The victims were members of the same family and they were collecting lotus leaves for a religious activity in a nearby kovil.
Police said 4 children are among the dead.
Two boys and two girls who were drowned were aged between 6 and 9 years.
Police said a 44-year-old person who manoeuvred the raft was also killed.
The area residents have rescued another small girl and she was admitted to Nilaveli Hospital.
However, one person has been rescued, police spokesman said.
Nilaveli Police is conducting investigations into the incident.
