The Electoral Commission of South Australia says it is investigating suspected voting irregularities in three local council elections, including "suspicious" enrolments and suggestions some ballots have been filled in by people other than those they were sent to.
Returned ballots from the Adelaide, Marion and West Torrens councils have been identified for further scrutiny, and efforts to investigate potential electoral fraud have included handwriting analysis and direct phone calls to voters to check whether they have cast ballots.
Counting of ballots is due to start tomorrow in council elections across the state.
South Australian council elections are conducted via a postal vote that ended yesterday.
Electoral Commissioner Mick Sherry has written to candidates in the affected council areas to inform them of the investigations.
He said 490 returned declaration envelopes in the City of Marion "appear to have been submitted by the same individuals".
"Our staff were scrutinising all the envelopes that had been returned to us and we identified that there was a large number of returned envelopes that had similarities, for example similar handwriting and the dates of birth weren't filled out," Mr Sherry said.
"It appears a person or persons unknown have got hold of ballot material that had been sent to electors and had filled it out on their behalf and sent it back to us."
The commission is still working out whether they will be counted tomorrow.
Rejected envelopes will not be opened.
In the City of Adelaide, the commission is scrutinising 90 envelopes after reports some ballot papers were collected from apartment buildings in the Central Ward.
Mr Sherry said it was alleged that "persons unknown had gone to four apartment buildings" and collected masses of ballots sent to voters.
"We've identified that approximately 364 electors were enrolled at those four apartment buildings. Whenever we received a ballot to our processing centre from one of those 364 we held it aside," he said.
"We've received at this point 90 returned ballots, out of those 364 enrolled electors, which we're subjecting to additional scrutiny."
Mr Sherry had previously refused to comment on the investigation, but today elaborated and confirmed that there was "concrete evidence" to justify concerns.
In the City of West Torrens, the commission is investigating enrolments on the supplementary voters roll, which is open to businesses and foreign citizens.
Mr Sherry said council staff had "identified quite a lot of unusual enrolment activity" and that 60 ballots were being scrutinised.
"We're looking at 109 suspicious enrolment transactions, of which we've received 60 returned ballots and we're conducting further additional scrutiny on those 60 ballots to determine whether they'll be admitted to the count or not," he said.
Premier Peter Malinauskas said he was "naturally concerned" but added that voters could still have "confidence in the process".
"The very fact that the Electoral Commission is undertaking these investigations speaks to the fact that we have processes and systems in place to ensure the integrity of election processes at a federal, state and also a local government level," he said.
Mr Sherry added that, in addition to the enhanced scrutineering already occurring, "significant investigations" would be conducted over the next two months.
"We'll work closely with the Crown Solicitor's Office in order to determine if the matter should proceed to prosecution," he said.
Along with the elections of mayors and councillors across the state, a plebiscite is being held on whether to merge the Mount Gambier and Grant councils in what could become a template for council mergers in the future.
Voting is not compulsory in council elections.
About one-third of the 1.2 million eligible voters have sent back their ballots.
