A laptop containing a copy, or “archive,” of the emails on Hillary Clinton’s private server was apparently lost—in the postal mail—according to an FBI report released Friday. Along with it, a thumb drive that also contained an archive of Clinton’s emails has been lost and is not in the FBI’s possession.

The Donald Trump campaign has already called for Clinton to be “locked up” for her carelessness handling sensitive information. The missing laptop and thumb drive raise a new possibility that Clinton’s emails could have been obtained by people for whom they weren’t intended. The FBI director has already said it’s possible Clinton’s email system could have been remotely accessed by foreign hackers.

The revelation of the two archives is contained in a detailed report about the FBI’s investigation of Clinton’s private email account. The report contained new information about how the archives were handled, as well as how a private company deleted emails in its possession, at the same time that congressional investigators were demanding copies.

The archives on the laptop and thumbdrive were constructed by Clinton aides in 2013, using a convoluted process, before her emails were turned over to State Department officials and later scrubbed to determine which ones had classified information and should either be withheld from public view or could be released with redactions. The archive of messages would contain none of those safeguards, potentially exposing classified information if it were ever opened and its contents read.

The FBI has found that Clinton’s emails contained classified information, including information derived from U.S. intelligence. Her campaign has disputed the classification of some of the emails.

The archive was created nearly a year before the State Department contacted former secretaries of state and asked them to turn over any emails that they had sent using private accounts that pertained to official business. A senior Clinton aide, Huma Abedin, told the FBI that the archive on the laptop and thumb drive were meant to be “a reference for the future production of a book,” according to the FBI report. Another aide, however, said that the archive was set up after the email account of a Clinton confidante and longtime adviser, Sidney Blumenthal, was compromised by a Romanian hacker.

Whatever the rationale, the transfer of Clinton’s emails onto two new storage devices, one of which was shipped twice, created new opportunities for messages to be lost or exposed to people who weren’t authorized to see them, according to the FBI report. (The Clinton campaign didn’t immediately respond to a request to comment for this story.)

The FBI found that in the spring of 2013, just after Clinton left the Obama administration, aides for Hillary and Bill Clinton worked together to create the archive.

Justin Cooper, who handled technology matters for the former president, provided Hillary Clinton aide Monica Hanley with an Apple MacBook laptop from the Clinton Foundation. Over the phone, Cooper “walked Hanley through the process of remotely transferring Clinton’s emails” from the server she’d been using as secretary of state, located in her home in New York, to the new “Archive Laptop,” as the FBI called it, as well as to the thumb drive.

“Hanley completed this task from her personal residence,” the FBI found.

The two copies of the Clinton email archive were supposed to be stored in Clinton’s homes, in New York and Washington, D.C. But, Hanley later told the FBI, that never happened, because she “forgot to provide the Archive Laptop and the thumb drive to Clinton’s staff following the creation of the archive.”

According to the FBI, months later, in early 2014, Hanley found the “Archive Laptop” at her personal residence and worked with another person to transfer the the emails to a technology company, Platte River Networks, which the Clintons had hired to manage the email system. (The name of the person helping Hanley is redacted in the FBI report, but appears to be an employee of Platte River Networks.)

After trying unsuccessfully to remotely transfer the emails to a Platte River server, Hanley shipped the laptop to the employee’s home in February 2014. He then “migrated Clinton’s emails” from the laptop to a Platte River server.

That task was hardly straightforward, however, and ended up exposing the email archive yet again, this time to another commercial email service.

The employee “transferred all of the Clinton e-mail content to a personal Google e-mail (Gmail) address he created,” the FBI found. From that Gmail address, he downloaded the emails into a mailbox named “HRC Archive” on the Platte River server.

Hanley told the FBI that she recommended Platte River “wipe the Archive Laptop” after the emails were transferred onto the company’s server. But the employee told investigators that while he deleted the emails from the laptop, he did not “wipe” it.

Emails deleted from an application might not be permanently erased. In fact, the FBI found nearly 15,000 emails that Clinton never turned over to the State Department, some of which had been deleted over time and were never found by Clinton’s lawyers. They ended up, among other places, in the “slack space” of servers Clinton had used, according to FBI Director James Comey.

The Platte River employee told the FBI that he deleted the emails from the Gmail account, but that turned out not to be entirely true. Investigators later found 940 emails sent or received in 2010 that, as of this past June, were still in the account. The FBI found that 56 of them have been identified as being currently classified at the “confidential” level.

After the employee deleted emails from the “Archive Laptop,” he shipped it by U.S. mail or UPS (he apparently couldn’t remember) to an unidentified Clinton aide at an office location. (The precise address is redacted.)

But that aide never received the laptop. She told the FBI that “Clinton’s staff was moving offices at the time, and it would have been easy for the package to get lost during the transition period.”

The thumb drive containing the second copy of the archive also was never found.

“Neither Hanley nor [the Platte River employee] could identify the current whereabouts of the Archive Laptop or the thumb drive containing the archive, and the FBI does not have either item in its possession,” the FBI report stated.

The FBI’s inspection of the Gmail account used to shuttle Clinton’s emails also turned up other concerns. Of the 940 emails still in the account, 302 “were not found in the set of e-mails” that Clinton eventually turned over to the State Department in December 2014, following the request that former secretaries produce their emails. Those may be some of the 15,000 emails that the FBI later discovered.

The FBI also found other instances in which Clinton emails were intentionally deleted. In or around December 2014 or January 2015, two of Clinton’s lawyers—Cheryl Mills and Heather Samuelson—decided they wanted to remove copies of Clinton’s emails on their own laptops. The copies has been placed there months earlier during a remote transfer from Platte River.

The FBI found that an unidentified individual (who again appears to be the Platte River employee) used a program called BleachBit “to delete e-mail related files so they could not be recovered.” The employee also told the FBI that an “unknown Clinton staff member” directed him to remove a backup file of the emails on the Platte River server. It’s not clear from the FBI report who that Clinton staffer was and why he, or she, decided to remove the backup, known as a .pst file, from the company’s server.

But after Clinton turned over copies of her email to the State Department, at the end of 2014, Mills decided to implement a new policy for keeping emails in the future.

According to Mills, who had also been Clinton’s chief of staff at the State Department, in December 2014, “Clinton decided she no longer needed access to any of her e-mails older than 60 days,” the FBI found. “Therefore, Mills instructed [the Platte River empoyee] to modify the e-mail retention policy on Clinton’s clintonemail.com e-mail account to reflect this change.”

But the Platte River employee didn’t make that change until the following March. Near the end of the month, in an “‘oh shit’ moment,” he told the FBI, he realized he’d forgotten to put the 60-day policy into effect. He then deleted the Clinton archive from the Platte River server and used BleachBit to delete any .pst file he had created containing Clinton’s emails. The FBI also found evidence that an alternate cloud backup had been manually deleted during the same timeframe.

This was not the best time to be erasing copies of Clinton’s emails. Earlier that month, The New York Times had first revealed that Clinton used a private server, and her email practices became a controversy that has dogged her campaign ever since. At the time, Clinton sought to downplay the issue, telling reporters in remarks at the United Nations, “I did not email any classified material to anyone on my email. So I’m certainly well-aware of the classification requirements and did not send classified material.”

But Clinton was under intense pressure to produce copies of her emails and prove she had never sent or received classified information; a claim that she frequently repeated but was later eviscerated by the FBI’s investigation.

But lawmakers were also curious about Clinton’s email system. The day after the Times story ran, the House committee investigating the 2010 terrorist attacks in Benghazi, Libya, asked Clinton’s lawyers to produce all emails related to her private accounts. And a week later, on March 9, Mills sent an email to the Platte River employee referencing that request.

The FBI appears to have investigated the question of whether the employee was directed to delete emails after the committee asked for them. Investigators discovered a “work ticket, which referenced a conference call on March 31, 2015, with Platte River, Mills, and David Kendall, Clinton’s longtime attorney who oversaw the process of separating her work emails from personal messages. It was Kendall’s firm, Williams & Connolly, that the Benghazi committee contacted when it wanted those official emails.

Platte River’s attorney advised the employee “not to comment on the conversation with Kendal based upon the assertion of the attorney-client privilege,” the FBI found.

Mills told the FBI “she was unaware that [the employee] had conducted these deletions and modifications in March 2015.” Clinton stated “she was also unaware” of the deletions.

But what exactly was discussed in that conference call, the FBI never found out.