Vellore parliamentary constituency recorded nearly 72 per cent polling on Monday, officials said.
There were no untoward incidents, police said, even as there were some reports of EVMs and VVPATs malfunctioning.
Tamil Nadu Chief Electoral Officer (CEO) Satyabrata Sahoo said "about 72 per cent" of the total 14.32 lakh voters cast their votes on Monday in the six Assembly constituencies covered under the Vellore Lok Sabha segment.
"The final figures are still awaited," he said.
The constituency is witnessing a fight between AIADMK and DMK, with A C Shanmugam of the ruling party taking on Kathir Anand, son of senior DMK leader Durai Murugan.
Counting of votes of will be taken up on August 9.
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The poll outcome is being keenly awaited as a win for the AIADMK would be seen as an endorsement of Chief Minister K Palaniswami's two year rule, although the party had little to boast of in the April 18 polls.
If DMK wins, it will be perceived as a verdict against the ruling party, with the state poised to face the general elections in 2021 at the end of the current term.
Both Palaniswami and Stalin had embarked on a hectic campaign schedule, fighting hard to reaffirm their respective parties' dominance.
Though polling was originally scheduled in Vellore on April 18 along with the rest of the 38 Parliamentary segments in Tamil Nadu, it was then rescinded after Income Tax officials seized money allegedly meant to bribe voters.
Earlier, the DMK-led alliance had swept the April 18 Lok Sabha elections in Tamil Nadu, winning 37 constituencies in the state and the lone segment in the neighbouring Puducherry.