The arrests were made based on a suicide note which stated that 'they (the family members) had taken loan and were under pressure to repay the same'.
The suicide note, recovered from the house where the family members ended their lives by consuming poison yesterday, also mentioned the names of the persons who gave the loan and threatened them, police said.
The deceased were identified as Manoharan (66), his wife Maheswari (61), and their sons Biju (36) and Saju (33) and Biju's wife Krishnenthu (24).
This had led the family to debt, according to the preliminary report of police.
Locals said debt collectors of the money lenders had repeatedly visited the house and threatened the family to clear the dues, which ran into lakhs of rupees.
Taking a serious view of the incident, state Home Minister Ramesh Chennithala had directed police to take stringent action against 'blade mafia' operating in the state, officials said.