Electoral commission CENI summoned candidates to a meeting in parliament on Thursday after media reports of a delay due to problems with vote materials.

Candidate Theodore Ngoy, who was at the meeting, said in a text message to Reuters that CENI president Corneille Nangaa announced the commission was “technically unable” to carry through the election as planned on Sunday.

The election is meant to choose a successor to DR Congo President Joseph Kabila, who is due to step down after 18 years in power, in what would be Congo’s first democratic transition.

There was no word on a new timetable, but Nangaa was scheduled to give a news conference at 3 p.m.

Earlier, another candidate Martin Fayulu told Reuters it would be unacceptable for the election to be pushed back.

“The CENI president said there will be an election rain or shine on the 23rd of December,” Fayulu said. “We cannot accept a change of Mr. Nangaa’s position today.”

Preparations for Sunday’s vote, already postponed repeatedly since 2016, were disrupted by a fire last week which the commission said destroyed 80 percent of Kinshasa’s voting machines.

On Wednesday, police fired tear gas to disperse rock-throwing opposition supporters in the capital after its governor ordered a halt to campaigning over security fears.

That decision was “manifestly illegal, we can’t respect it,” said Fayulu, one of 21 candidates.

Campaigning had been due to end at midnight on Friday in what has boiled down to a race between Kabila’s preferred successor, Emmanuel Ramazani Shadary, and two main challengers, Fayulu and Felix Tshisekedi.