Austria’s rerun presidential election, scheduled for 2 October, may be postponed on technical grounds because of problems with glue on postal votes coming unstuck, the country’s interior ministry has said.

The election was originally held in May but the constitutional court ordered a repeat poll after the far-right Freedom party (FPO) successfully challenged the result due to procedural irregularities.

The FPO candidate, Norbert Hofer, narrowly lost that vote to the former Green party leader Alexander Van der Bellen, who was running as an independent. Hofer has led in recent opinion polls.

“If an apparent failure in production makes it impossible to properly conduct the election, then it is my duty as the highest-ranking executive of the electoral authority to immediately consider a postponement,” the interior minister, Wolfgang Sobotka, said in an emailed statement.

An interior ministry spokeswoman said a decision was expected early next week.

Over the past few days several eligible voters from cities including Vienna and Salzburg have complained about damaged ballot papers. About 500 damaged papers have been detected so far, according to the daily Die Presse. The printing company KBPrintcom, which was commissioned by the interior ministry, declined to comment on the issue.

Experts have warned the results of the new election could be challenged again. If a ballot paper becomes invalid through no fault of the voter “that would be surely a reason for contesting the election if there is a narrow result”, the political analyst Peter Filzmaier said.

An FPO spokesman said the party was relaxed about the issue. “We assume that the election will be run properly,” he said. “We do not wish for another challenge.”

Van der Bellen called for a prompt clarification of the situation late on Thursday, telling the broadcaster ORF that every eligible voter should be able to rely on their vote being counted.

Van der Bellen has been catching up in the race but is still behind his anti-immigration rival, according to an opinion poll by the researcher Gallup.

The former professor, perceived as the intellectuals’ representative, has been travelling to public festivals and fairs in recent weeks seeking support from farmers and blue-collar workers.

A poll of 600 people on 7-8 September, published by the Österreich tabloid on Friday, showed the average support for Van der Bellen at 48%, only slightly higher than a poll in late August, against 52% for Hofer.

Concerns about security and national identity as well as dissatisfaction with traditional, more centrist parties, have fuelled support for the FPO as well as the Front National in France and the far-right party Alternative for Germany.