WASHINGTON — The F.B.I. on Monday began loading a trove of emails belonging to a top aide to Hillary Clinton into a special computer program that would allow bureau analysts to determine whether they contain classified information, law enforcement officials said.
The software should allow them to learn relatively quickly how many emails are copies of messages they have already read as part of the investigation into the use of Mrs. Clinton’s private server. The F.B.I. completed that investigation in July and, along with prosecutors, decided not to bring any charges against Mrs. Clinton or her aides.
Whether investigators will be able to complete their review by Election Day is unclear, although they have been under intense pressure from officials in both parties to do so since Friday, when the F.B.I. director, James B. Comey, revealed the existence of the emails in an explosive letter to Congress.
Robert E. Anderson Jr., a former senior F.B.I. executive, said it could take less than a day for the program to identify duplicates. He said that the program would organize the duplicates in a special folder and that F.B.I. agents and analysts would then check each of them to make sure they were indeed copies.
Should the F.B.I. find emails it has never seen before containing potentially classified material, copies would have to be sent to other government agencies to determine their classification — an elaborate and lengthy process.
The emails belong to Huma Abedin, the aide to Mrs. Clinton. Agents discovered them on a laptop seized by the F.B.I. that belongs to Ms. Abedin’s estranged husband, Anthony D. Weiner, who is under investigation on allegations that he exchanged illicit text messages with a 15-year-old girl.
While the hunt for classified information is the bureau’s first priority, it is not the most significant issue for either Ms. Abedin or Mrs. Clinton. Investigators have already determined that Mrs. Clinton and her aides improperly sent classified information on her private email server. The Justice Department concluded, though, that it could not prove they did it intentionally, which would be a crime. Finding more classified information among Ms. Abedin’s emails would not immediately change that conclusion.
The agents will also focus on whether this new material contains any evidence that anyone may have tried to conceal these newly discovered emails or others from investigators, which could amount to a crime. Ms. Abedin has said she turned over all her emails to the F.B.I. months ago and does not know how emails ended up on Mr. Weiner’s laptop. Officials have said in the past that there is no indication that Ms. Abedin or Mrs. Clinton tried to conceal information from the authorities.
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As part of that inquiry, the agents built a system that allowed them to examine thousands of emails to see whether they contained sensitive national security information. When the agents identified potentially classified materials, they sent copies of the emails to other government agencies to determine their classification.
The emails the F.B.I. is now searching could well be like scores already made public by the State Department under the Freedom of Information Act, including some of the additional ones uncovered by the bureau’s investigation and turned over to the department this summer.