OTTAWA -- Justin Trudeau's Liberals have picked up one more seat in Quebec, pushing them slightly ahead of the Bloc Quebecois in the province.

Brome-Missisquoi is the only riding so far to change hands since Monday's preliminary election results, which did not include some 850,000 mail-in ballots.

Once election officials finished counting postal votes in the riding Thursday, Liberal Pascale St-Onge edged ahead of the Bloc's Marilou Alarie by just 186 votes.

That leaves the Liberals leading or elected in 34 of Quebec's 78 seats, to the Bloc's 33 and also puts them slightly ahead in terms of the popular vote.

The Conservatives are leading or elected in 10 Quebec ridings and the NDP in just one.

Nationally, the Brome-Missisquoi victory puts the Liberals at 159 seats, although one of them was won by a disavowed Liberal candidate -- Kevin Vuong in Toronto's Spadina-Fort York -- who will now have to sit as an Independent MP.

With the mail-in ballot count still continuing in four tightly-contested ridings Thursday evening, the Conservatives stood at 119 seats, the NDP at 25 and the Greens at two.

However, recounts are expected in a clutch of close-run ridings, where a handful of votes separates the victor from the loser.

In most ridings in Quebec, Ontario and Atlantic Canada, counting was complete by Thursday afternoon, as well as in the Yukon and Northwest Territories.

But across B.C. -- where more mail-in ballots were received than any other province -- election officials were still tallying thousands of votes.

As the remaining results rolled in, election experts warned that, in a few photo-finish ridings, a recount will have to settle who ultimately sits in Parliament.

Experts say a recount is expected in the Winnipeg-area riding of Charleswood-St. James-Assiniboia-Headingley where Conservative Marty Morantz beat Liberal Doug Eyolfson by just 24 votes.

Elections Canada said on Thursday afternoon that counting had finished there and results were being verified.

A judicial recount would likely be triggered there because the margin is so small, experts said.

Quito Maggi, a pollster who runs public opinion firm Mainstreet Research, said voters should expect recounts in a number of ridings.

"The Charleswood seat is heading for a judicial recount. I suspect that at least two or three other (candidates) will ask to go to recount," Maggi said.

"We noticed at this election that there were a larger number than expected close races. The turnout was way, way down too. At least 1.2 million fewer people voted in this election than the last election."

An automatic judicial recount is triggered if there is a tie between the two leading candidates or if the difference in votes is fewer than one one-thousandth of the total votes cast.

In other tight races, the loser has the option to go to court to ask for the votes to be counted again. The NDP, Conservatives and Liberals did not say, when asked by The Canadian Press, whether they would demand recounts in ridings where they have come second by a tiny margin of votes.

Among the close-run results is in Sault Ste. Marie, Ont., where less than one per cent of the vote separates the Liberals and the Conservatives. Liberal Terry Sheehan narrowly fought off Tory Sonny Spina by 247 votes after mail ballots were counted.

In Vancouver Granville, another close race, the counting of mail-in ballots continued on Thursday, although CTV News has declared the riding for Liberal candidate Taleeb Noormohamed. As of Thursday afternoon, Noormohamed had 258 more votes than New Democrat Anjali Appadurai.

In the Davenport riding in Toronto, the Liberals' Julie Dzerowicz won by fewer than 200 votes, after a close-fought challenge from the NDP.

The NDP snatched Edmonton Griesbach from the Tories, with a greater than expected margin, after a dynamic campaign by two-spirit Metis leader Blake Desjarlais.

Similarly, Liberal Patrick Weiler emerged Thursday from the mail-in count with a lead of almost 2,500 votes ahead of his Conservative rival in B.C.'s West Vancouver-Sunshine Coast-Sea-to-Sky Country.

Elections Canada expected more ridings to finish counting mail-in ballots Thursday night. But in some with thousands of postal votes -- many of them in B.C. -- counting will continue on Friday.

On Thursday evening, several B.C. ridings, including Nanaimo-Ladysmith, which is the site of a fierce battle between the NDP, Conservatives and Greens, were still counting.

In Victoria, elections officials were busy tallying up more than 12,600 ballots sent in by mail -- the most in Canada.

Counting was also progressing in Saanich-Gulf Islands, where over 10,700 people have opted for postal votes and Elizabeth May, the former Green party leader, was on Thursday declared the winner.

On Thursday night, CTV News' Decision Desk has declared Liberal Wilson Miao the winner in Richmond Centre, B.C., defeating veteran incumbent Alice Wong.

Elections Canada said it expected counting to be completed in almost all ridings by Friday.

This report was first published by The Canadian Press on Sept. 23, 2021.

With files from CTV News.