Montreal election officials say they have had difficulty compiling and transmitting election results. (CBC)

Montreal election officials say it is unclear when the final results of Sunday’s municipal election will be announced.

Delays in many of the results from Montreal's municipal election on Sunday were caused by communication problems between polling stations and the central counting centre, said the city's election agency.

Agency spokesman Pierre G. Laporte said some progress had been made Monday, but could not say how long it would take for the final results to be released.

"I agree, it is taking a long time," Laporte said.

Laporte could not specify how many districts were still affected by the problem.

Election workers still had to compile and transmit results from about 27 per cent of the city’s polling stations, agency president Yves Saindon said in a news release Monday morning.

Some stations stayed open beyond 8 p.m., because voting started late on Sunday morning.

The agency decided to suspend compiling of results at 3 a.m. on Monday morning to allow workers to get some sleep.

Several candidates running on the island of Montreal still don't know the final results from Sunday's election.

However, the Montreal mayor's race was decided Sunday night.

Incumbent Gérald Tremblay was re-elected with a modest margin of 37.5 per cent of the vote, while Vision Montréal hopeful Louise Harel garnered 32.9 per cent of the vote.

Projet Montréal's leader, Richard Bergeron, was third with 25.7 per cent of the vote, while Louise O'Sullivan earned two per cent.