Papua New Guinea's electoral commissioner says he will conduct an investigation into allegations of widespread voter fraud.
As PNG's election limps into its second week, electoral commissioner Andrew Trawen has defended his agency's handling of the 2012 elections. Producing a clean electoral roll was difficult because of widespread fraud, he said.
Many voters have complained their names are not on the roll at some voting booths.
Mr Trawen acknowledges fictitious names are also a concern amid allegations names appearing on the preliminary roll were not on the final roll.
"It is very difficult to produce a roll with the highest level of accuracy and integrity when some people are prepared to go to any length to corrupt the process," he told The National newspaper.
"We have found evidence of deliberate actions by some to remove names, add names and modify the status of persons.
"Once we have completed our inquiries, I will refer these matters to the police."
Prime Minister Peter O'Neill last week called on Mr Trawen to release the preliminary roll following reports of delays at polling booths in the nation's capital, Port Moresby.
Mr Trawen did not release the preliminary roll. Neither he nor Mr O'Neill could be reached for comment.
Bill Gardner, a candidate for the governorship of the newly created province Jiwaka, said he was concerned about the management of the roll.
"Between the preliminary rolls going to Moresby and the roll then coming out of Moresby, that's where the foul play happened," he told AAP.
"It's going to cause a fair bit of grief in areas up here. We have situations where somebody isn't on the roll, but they are on the roll in another tribe's area.
"In Moresby that might be OK, but up here you have village people who've been living in one area their whole life and find out they're on the roll 10 miles away, but can't go there because of tribal issues."
Jiwaka is due to head to the polls on Tuesday.
Early counting shows Mr O'Neill is set to return to parliament in 2012, with the incumbent PM leading his Ialibu-Pangia electorate with 7778 votes, according to the PNG electoral commission website.
His closest contender is independent Eke Lama with 1524 votes.
Counting began in the Southern Highlands, home to Mr O'Neill, late last week.
Polling in Western Province began on Monday; at the same time, polling in the National Capital district is expected to end.
Polling in PNG began in the Southern Highlands and Hela provinces last week amid a massive security operation by police and military.
Authorities have to drive, fly and sometimes walk ballot boxes through often impassable terrain.
Voting is expected to end on July 6.