The vote count for Harvard’s historic student union election will stretch into December, as University officials and union organizers worked through challenged ballots on Tuesday and will reconvene on Friday to continue sorting through the challenges.

As a result, ballot boxes with student votes have remained sealed for nearly two weeks since the mid-November voting period, which is standard protocol until all of the questions surrounding challenges are resolved. The election is being supervised by the National Labor Relations Board.

Votes are challenged at the time of the election and set aside if there are questions about voter eligibility, whether the voter submitted their ballot at an unassigned location, or whether the ballot matches the name on the list of eligible voters for a given location. Approximately 3,500 graduate and undergraduate students were eligible to vote in the election, according to Graduate School of Arts and Sciences spokesperson Ann Hall.

While hundreds of the estimated 1,000 challenges have been resolved, more challenges remain to work through, according to the Harvard Graduate Students Union-United Auto Workers’ Facebook page.

“We’re making progress, but it’s slow,” NLRB deputy regional attorney Robert P. Redbord said. “We’re hopeful that we might be able to do something later in the week, but not before Friday at the earliest.”

The same post on the HGSU-UAW’s Facebook page confirmed that organizers will return to the NLRB’s Boston office on Friday to resume the work.

The count could extend into next week, as graduate and undergraduate student teaching and research assistants at Columbia head to voting booths for their Dec. 7 and 8 union union election. Like Harvard's union effort, Columbia’s graduate student union effort is affiliated with the United Auto Workers.

In an email sent Nov. 23 to eligible voters, Director of Harvard’s Office of Labor and Employee Relations Paul R. Curran wrote, “Because this is the first such election, the number of challenge ballots is not surprising.”

“The University respects the votes cast by students in this consequential election and, along with many others across our community, we are committed to ensuring that the ballots of all eligible voters are counted,” Curran wrote.

Harvard is the first university to hold an election after the NLRB ruled in August that teaching and research assistants are employees under labor law, and entitled to collective bargaining rights.

—Staff writer Leah S. Yared can be reached at leah.yared@thecrimson.com. Follow her on Twitter @Leah_Yared.