State Department officials released 350 deleted emails from Hillary Clinton's private server Thursday amid controversy over the FBI's decision to reopen its investigation of her treatment of classified material.

The agency said the 1,250 pages of documents were mostly "near duplicates" of emails published earlier this year and last year.

Those email chains were at least partially included in the 55,000 pages of records Clinton turned over to the State Department in Dec. 2014.

But others were withheld from the agency, despite Clinton's assertion that she had provided all of her work-related emails to the State Department.

The FBI recovered roughly 15,000 emails during its year-long probe of Clinton's server. Agents handed over those emails to the State Department after FBI Director Comey closed the investigation in July.

Of the 15,000 emails, 9,400 were deemed personal in nature and withheld in their entirety. The State Department said up to half of the remaining records could be duplicates of those already released, meaning at least 2,800 of those emails were deleted by Clinton's team despite being related to her work as secretary of state.

The emails released Thursday afternoon marked one of the final troves of Clinton records set for publication before the election. Monthly document dumps dogged Clinton's campaign from May 2015 to February of this year, and began again in early October as the State Department began preparing the FBI-provided material for release to the public.

Clinton has struggled to answer questions this week about Comey's announcement that new emails had prompted his agents to take "investigative steps" in the case he had closed more than three months earlier.

Investigators reportedly discovered the thousands of new emails on at least one device shared by Huma Abedin, vice chair of Clinton's campaign, and her estranged husband Anthony Weiner.

Weiner is under FBI investigation for unrelated allegations of sexual misconduct involving an underage girl.