Former state Sen. Mark Leno this afternoon remains in the lead in the tight race for San Francisco Mayor.
Leno advances but with only 1,121 more votes than the President of the San Francisco Board of Supervisors London Breed.
As of 4 p.m., Leno has received 71,126 votes, claiming 50.40 percent of the vote, and Breed has received 70,005 votes, or 49.60 percent of the total. The latest results include vote-by-mail ballots received by mail on Tuesday.
Election officials have cautioned that they "will need to review and process most of the remaining 90,000 ballots over the next few weeks."
The Elections Department said the uncounted ballots include about 44,000 vote-by-mail ballots delivered to local polling places on Election Day Tuesday and about 14,000 provisional ballots.
Voters dropped off an additional 3,000 vote-by-mail ballots at stations outside City Hall on Tuesday.
Elections Director John Arntz said he expected the U.S. Postal Service to deliver 13,000 ballots today.
The department will continue to process additional mail ballots that are postmarked by June 5 and received by Friday.
Arntz said updates will continue daily at 4 p.m., including over the weekend. He said his department hopes to process most of the mail ballots by Sunday.
"We put them in trays, we put header cards in there to indicate what batch they’re from," said Arntz.
The mayoral vote reflects San Francisco ranked-choice voting, in which voters mark their first, second and third choices. As candidates with fewer votes are successively eliminated, their supporters' votes are given to their other choices.
San Francisco native Breed, 43, grew up in public housing and previously worked as executive director of the African American Art & Culture Complex. She was first elected to the Board of Supervisors in 2012 and was re-elected in 2016.
Leno, 66, served as a San Francisco supervisor from 1998 to 2000, before being elected to the state Assembly in 2002, and then to the state Senate in 2008.
The winner of the mayoral race will serve the remainder of the late Mayor Ed Lee's term, which runs through January 2020. Lee died unexpectedly in December.
Mayoral candidate Supervisor Jane Kim, who has been eliminated from the contest, said in a statement, "Right now it looks very likely that Mark Leno will be elected San Francisco's next mayor.
"Out of respect for the ballots still being counted and received, we will wait for a final announcement, but should these returns hold true, I look forward to working with this administration and I've called him and congratulated him on these early results."
Sam Brock contributed to this article.