Voting was underway at the African National Congress' OR Tambo regional conference on Sunday morning, the ANC said in a statement.
"Delegates to the OR Tambo ANC Regional conference have just started voting for members to the top five positions of the Regional Executive Committee," said ANC Eastern Cape chairman Pumulo Masualle.
"[This follows] the successful resumption of the conference yesterday evening."
The King Sabatha Dalindyebo sub-region was the first to cast their votes, with voting beginning after 5am on Sunday.
"Upon resumption the conference discussed the report tabled by the Conference Steering Committee about the discrepancies picked up from the credentials of the adjourned conference," said Masualle.
Delegate numbers were affirmed at the conference, with 582 out of 588 delegates attending.
He said, "Names and positions of the candidates contesting the top 5 positions have been billed in one ballot paper and each voting delegate will use 1 ballot paper to vote for the top 5 candidates."
Voting duplication would be avoided via thumb prints, with delegates voting per sub-region. Security was present around the voting stations.
Results were to be announced later on Sunday morning, with voting expected to be completed by 10am.
Earlier this month, the original regional conference was adjourned before new leaders could be elected. Its shutdown came after allegations that membership figures were inflated, and that there were several "ghost" delegates.
The outcome of the region's election would be integral to President Jacob Zuma's bid to retain the leadership of the party at its national congress in Mangaung in December.
The region is the largest in the Eastern Cape, and the second largest ANC region in the country, after eThekwini in KwaZulu-Natal -- Zuma's home province.