The error is widespread and has affected polling stations in almost all of Sweden. During the night of Friday, the error was stopped and voting is continuing as planned.
"We will come back with more information as soon as we know, but we need some time to analyse. But we can see that it is a very serious incident," says Anna Nyqvist, the Election Authority's chief of staff, to TT.
Didn't understand
On Tuesday afternoon, the authority received information from Nynäshamn Municipality, which had discovered the error, but it was only on Thursday that the Election Authority began investigating the error, reports P4 Stockholm .
"You can always be wise in hindsight, but we didn't understand the extent and there are a large number of incidents that come to us," Nyqvist tells the radio.
The cause is a technical error, and there are no signs of external influence, according to Nyqvist.
The authority is now working with the IT provider and the Swedish Tax Agency to minimise the consequences for the election results. Some of the voters will be able to be identified. Votes that cannot be identified will be rejected.
"We understand that there is concern and we are working intensively to identify as many of those affected as possible. That's 4,000 out of 1.4 million, it's a serious error but it affects a small portion of the voters who voted," Anna Nyqvist tells TT.
Then the vote becomes invalid.
Can worried voters fix the problem by voting again on Election Day?
I don't want to answer that yet because I want us to have progressed further in the analysis work so I know how many voters it concerns.
However, voters should not vote early more than once.
"If you vote early several times, all early votes will be invalid," the authority writes on its website .
What do you think?