As of 1 p.m., 45.78 per cent voter turnout was recorded, said CEO Kunal.
Voting began at 7 a.m. with 22,482 voters eligible to cast ballot, of which 10,697 are male and 11,785 female.
Bharatiya Janata Party's (BJP) Sidharth Kunclaienkar is pitted against Atanasio Monserrate of the Congress, Valmiki Naik of the Aam Aadmi Party (AAP) and Subhash Velingkar of the Goa Suraksha Manch in the contest for the prestigious Panaji Assembly seat, which the BJP has held since 1994.
Velingkar and Kuncalienkar have exercised their franchise.
"The BJP has gone to the lowest levels to defame me. People will pay them back while polling today," Velingkar told reporters.
"Panaji's voters are all set to choose the BJP, as it is the only option which can provide development," Kuncalienkar said.
Congress candidate Monserrate, who has been charge sheeted in a minor's rape case, said the BJP has tried to assassinate his character during the poll campaign.
The "The judge who is hearing the case will decide my character. The voters will vote on the basis of the manifesto I presented and my track record," he said.
The bypoll has been necessitated due to the death of former Chief Minister Manohar Parrikar on March 17, after a prolonged battle with pancreatic cancer. Goa already witnessed by-elections to three other Assembly seats and two Lok Sabha constituencies on April 23.