While Natarajan died because of heat, the other two died of cardiac problem, the police said.
Three DMK workers who came to participate in the 10th State conference of the party here, died outside the pandal at the venue on Sunday.
The names of the dead were given as Natarajan (70), a former teacher from Thammampatti in Salem district, Kamaraj (50) of Srikaragur village near Palakkod in Dharmapuri district, and T. Krishnan (55) of Thanthonrimalai in Karur district.
While Natarajan died because of heat, the other two died of cardiac problem, the police said. Kamaraj was listening to the speeches from his car parked in the venue when he was found dead.
Inside the venue, sparks from an electric wire caused a flutter for some time right behind the press enclosure.
The incident took place when the resolutions were being read out by the party organising secretary T.K.S. Elangovan.
Some of the cadre apparently pulled the wire tied to a pole causing it to burn.
A portable smoke extinguisher was put to use. Power connections to the arc lights were immediately snapped and the teeming cadre were asked to move to a distance from the spot.