48-year-old Vasu, who died yesterday, had already undergone a bypass surgery and was not supposed to be put on tough jobs, police said.
He fainted while on duty and was rushed to the government hospital at Madurai, but died en route, they said.
DIG Amalraj ordered to enquiry to ascertain whether Vasu had volunteered to work or he was forced to work near the helipad, the sources said.
