Clayton Harris keeps chiseling away at Eileen O’Neill Burke’s lead in the race for Cook County state’s attorney as Chicago election officials continued counting mail-in ballots Sunday.

Burke’s slim lead over Harris was trimmed to 2,015 votes after more ballots from Chicago voters were tallied. Harris closed the gap with a net gain of 2,756 votes.

The two were separated by 4,771 votes after ballots were counted Saturday. Harris trailed by about 10,000 votes after Tuesday’s election.

Based on the unofficial count results, Burke is leading Harris, 50.19% to 49.81% overall, with thousands of mail-in ballots still to be counted in the city and suburbs.

Harris, a university lecturer, has maintained a narrow edge among Chicago voters, and Burke, a retired appellate court justice, has enjoyed a comfortable lead in the suburbs so far.

The Cook County election board has not released new numbers from its count of mail-in ballots from suburban voters since Thursday.

The Chicago Board of Election Commissioners on Sunday said there are 54,191 outstanding mail-in ballots that were sent out to voters yet to be returned, and officials don’t expect to receive them all.

About, 2,500 mail-in ballots will be processed and counted Monday, Chicago election officials said. The process should continue in much the same manner until the April 2 deadline. Updates to the totals are expected to be released each day. Election officials have said they will count any ballot that arrives by April 2, provided it was postmarked no later than Election Day.

On Saturday, city election officials unexpectedly announced that roughly 10,000 votes were added to the unofficial count. Max Bever, Chicago Board of Elections spokesman, said in a statement that he had mistakenly left out ballots received by mail Monday evening, the day before the primary, in the previous totals.

“I traded speed for accuracy in reporting out numbers this week as quickly as I could,” Bever said. “I truly regret this error on my part and for the confusion that it has caused the voters of Chicago.”

Bever said those mail ballots were kept under lock and key until they could be verified.

Both campaigns were informed of the error, Bever said. Poll watchers for the two candidates were present during Sunday’s counting.

In a statement, Burke’s campaign said, “We have a vigilant team of volunteers, lawyers and retired judges who are watching the vote count process at the Board of Elections very closely.”

Alaina Hampton, Harris campaign manager, also said they were keeping a close watch on the process.

“As the votes are processed and the margin in this race continues to shrink, we are watching closely and evaluating our options,” Hampton said.

The county election board is processing suburban mail-in ballots separately. A spokesman for that board has said updated results were not expected until early this week.

The large number of mail-in ballots and the closeness of the race has kept a winner from being called. Neither campaign has claimed victory or conceded defeat, instead urging supporters to be patient and allow the democratic process to play out.

The current state’s attorney, Kim Foxx, announced last year she was not running for re-election. The winner of the Democratic contest will head into the fall general election as the overwhelming favorite over Republican Bob Fioretti.

The race between Harris and O’Neill Burke was viewed in many circles as a referendum on Foxx’s progressive policies, which have drawn criticism from the right as being soft on crime, and praise from the left as addressing generations of inequity in the criminal justice system.

Contributing: Matthew Hendrickson