One Nation candidate Chantelle Thomas has increased her majority in the South Australian seat of Narungga after election officials uncovered dozens of previously uncounted ballot papers. 

The Electoral Commission of South Australia ordered a recount after discovering 81 overlooked votes, only weeks after the razor‑thin result had been declared. 

Thomas had been declared the winner on April 2, defeating Liberal opponent Tania Stock by just 58 votes following an initial recount - a margin dwarfed by the inclusion of the uncounted ballots.

The stash included 77 unopened absent ordinary ballot papers and four declaration ballot papers mistakenly returned to the commission with votes inside.

All were located in three sealed boxes linked to Narungga and neighbouring Stuart.

But following the second recount, One Nation leader Pauline Hanson declared that Thomas was still victorious - this time with an increased margin. 

'The recount for the seat of Narungga, South Australia, where a missing box of ballot papers was found has been completed,' Hanson wrote on social media on Friday. 

'I want to congratulate One Nation's new MP Chantelle Thomas as she has increased her margin of victory from 58 to 73 votes after the count.

Hanson said there would now be seven One Nation MPs in the new South Australian Parliament, to be led by Cory Bernardi as parliamentary leader. 

The result was confirmed by South Australia's acting electoral commissioner Leah McLay.

'A count of Narungga ballot papers retrieved from the district of Stuart occurred at the Electoral Commission this morning,' she said in a statement.

'The purpose of the count was for the Commission to determine whether the result in Narungga would have differed, had those ballots been included in the initial count and subsequent recount.'

The organisation stated that, of the 81 ballots, one was rejected while the remainder were deemed informal. 

'Of the 76 votes counted in a two-party preferred count, 46 were for Chantelle Thomas, One Nation and 30 were for Tania Stock, Liberals,' it said.

'Had the ballot papers been included in the original count and subsequent recount, the margin in favour of Chantelle Thomas One Nation would have increased from 58 to 74.

'I have therefore determined that the result in Narungga would not have differed had the ballots been included.'