Challenger Zac Blanchard took a 28-vote lead over incumbent Eric Costello in the race to represent South and Central Baltimore neighborhoods in the city’s 11th District as the third day of mail ballot counting closed on Tuesday.

Meanwhile, Paris Gray and Jermaine Jones maintained the thin leads they had established since the end of election night in the 8th and 12th districts.

“Though we’re excited, there’s plenty of votes left to be counted,” Blanchard said late Tuesday afternoon. On Wednesday, canvassers will begin reviewing at least 6,000 additional provisional ballots — which are ballots that require manual review to verify a voter’s eligibility — and elections officials expect to use the rest of the week to tally up those votes, board of elections representative Tamara M. Debnam said Tuesday.

Canvassers spent Tuesday counting more than 5,400 mail-in ballots from across the city. The latest batch of unofficial results pulled from counting machines at the warehouse show Blanchard has 3,246 votes to Costello’s 3,218.

Jones, meanwhile, ended Tuesday with 229 more votes while incumbent Robert Stokes Sr. won 95 of the latest batch, giving Jones a 383 vote lead. Gray, outgoing City Councilman Kristerfer Burnett’s community outreach coordinator, earned 157 of Tuesday’s tally while former state Del. Bilal Ali won 94, giving Gray a 211 vote lead.

The slow, tedious process of counting every vote has set off extra frustrations from candidates this year. Already, Blanchard said he has considered retaining an attorney due to “a couple issues” he had noticed with the election process this year.

“And in the event of a very close finish (which seems likely),” Blanchard wrote in a Saturday email, “we will be requesting a full recount to ensure all the 11th district’s ballots were properly counted.”

Elections officials said last week that a “human error” caused a temporary inflation of about 590 votes interspersed throughout city government races. The discrepancy surfaced after a standard verification audit of one of the steps involved during counting, when unofficial results are compared against log reports from each polling center. By late Friday, a statement from the board said they were confident the votes canvassed up to this point were done so accurately.

City Election Director Armstead Jones said Thursday a memory stick was found earlier that day that may have impacted the results, but that no candidates “should have lost anything.”

An independent, third-party firm has conducted its own audits of the results, which is available on the board’s website.

This article has been updated to correct the number of Jermaine Jones' district.