Voting hours for the district council elections were extended to midnight due to an electronic poll register system failure, officials said on Sunday.

Instead, all polling stations have been using printed copies of the voter register to issue ballot papers since 8.12pm.

“The polling hours will be extended accordingly,” election officials said.

Polling stations for geographical constituencies were originally slated to close at 10.30pm.

David Lok, chairman of the Electoral Affairs Commission (EAC), apologised for the incident that he described as "unfortunate", saying that the system malfunctioned at 7.42pm and that authorities are looking into it.

"At this stage, there is no evidence to suggest there has been a cyber attack," Lok told reporters.

"The only thing we hope for is that the elections could be conducted in an orderly and fair manner. We think extending the voting hours by one and a half hours is a relatively reasonable arrangement, taking into account the delivery of the message, and whether voters would be affected."

Lok also stressed that extending voting hours would not result in more people deciding to vote.

Tony Wong, the government's chief information officer, said a preliminary check showed that there had been a problem with the system's back-end database.

He said authorities decided to switch to printed voter register after 15 minutes of investigating.

"The overall network is normal, and there isn't any unusually high traffic or something unusual like a cyber attack," Wong said, adding there are measures in place to avoid repeated voting.

A man told RTHK that he experienced the system failure when he was about to vote.

"It was smooth, but I had to wait for a while," he said.

A woman, surnamed Tung, said she waited for half an hour before voting.

"There were only four people per queue, but each of them took five minutes," she added.