The State Department asked a federal court Friday for a one-month extension to publish the last of Hillary Clinton’s emails during her time as secretary of state, citing a complex review of some messages across different agencies of the government.

State Department spokesman Mark Toner said the department wouldn’t be able to meet its court-mandated goal of Jan. 29. About 9,400 of 55,000 pages are left, but Toner said those remaining “contain a large amount of material that required interagency review.”

The department will make public as many as possible next week, he said, but is asking for the final deadline to be pushed back until Feb. 29.

“State Department staff have been working extremely hard to process these emails, and we are committed to getting them out,” Toner said. “The court’s goal for this month’s production represented the largest number of pages to date. The remaining emails are also the most complex to process.”

Some of the most contentious emails haven’t yet been published. They include two that an intelligence community auditor says are “top secret” and others he claims are even more sensitive, containing information from so-called special access programs. Such programs suggest the emails could reveal details about intelligence sources.

The State Department says no emails published so far contained material with “top secret” information or any material that was marked classified at the time. The issue has nagged at Clinton’s presidential campaign, with the FBI said to be examining in some capacity.

Toner said the delay in publication isn’t the result of “ongoing discussion about classification” that has been made public recently. He said he couldn’t comment further on ongoing litigation.

Clinton, the Democratic front-runner for the 2016 nomination, exclusively used a private email account and a home server during her time in government. She said this was a decision made out of convenience and has denied doing anything wrong.

(AP)