The US Secret Service produced an "initial set of documents" to the House select committee investigating the January 6, 2021, insurrection on Tuesday, in response to a subpoena last week that was issued amid reports of potentially missing text messages from the day of the insurrection.

"Our delivery included thousands of pages of documents, Secret Service cell phone use and other policies, as well as operational and planning records," USSS spokesman Anthony Guglielmi said in a statement.

However, Tuesday's document production didn't include any of the potentially missing texts from January 5 and 6, 2021, a Secret Service official told CNN. That's because the agency still has not been able to recover any records that were lost during a phone migration around that time, the official said.

"Any message that was not uploaded by the employee as a government record would have been lost during the migration," the USSS official told CNN, referring to the agency's backup procedures.

Before the phone migration, Secret Service employees were supposed to manually back up their text messages. If any employees skipped that step, their texts would have been permanently deleted when their phones got wiped during the migration.

The Secret Service insists that it is still trying to recover any lost messages.

"We continue to scrutinize our records, databases, and archives to ensure full compliance with the Committee's subpoena," Guglielmi said in a statement. "We are taking all feasible steps to identify records responsive to the subpoena, to include forensic examinations of agency phones and other investigative techniques."

The Secret Service informed the committee Tuesday that it is "currently unaware" of any text messages that were not retained, according to a source familiar with the Secret Service communication with the committee.

"We are currently unaware of text messages issued by Secret Service employees between December 7, 2020 and January 8, 2021 requested by OIG that were not retained as part of the Intune migration," the agency wrote to the committee.

Congress informed the Secret Service it needed to preserve and produce documents related to January 6 on January 16, 2021, and again on January 25, 2021, for four different committees who were investigating what happened, according to the source. The Secret Service migration did not start until the January 27, 2021.

"Nobody along the way stopped and thought, well, maybe we shouldn't do the migration of data and of the devices until we are able to fulfill these four requests from Congress," said Democratic Rep. Stephanie Murphy of Florida, a committee member, in an interview on MSNBC. "The process as explained to us was simply to leave it to the agent to determine whether or not there was anything on their phones worth saving that was necessary to save for federal records."

Separately, a source familiar with the matter told CNN that employees were instructed twice to back up their phones.

Secret Service employees were told in December 2020 and again in January 2021 that if they were going to back up their phones, they'd need to do it manually, a source familiar told CNN. The source said employees were given instructions on how to do the manual backup.

Earlier Tuesday, the National Archives joined a growing list of federal agencies and officials demanding answers about the batch of missing text messages.

Laurence Brewer, the Chief of Records officer for the US Government sent a letter to the Department of Homeland Security Records officer on Tuesday asking the agency to clear up if the text messages were deleted and explain why.

"If it is determined that any text messages have been improperly deleted (regardless of their relevance to the OIG/Congressional inquiry of the events on January 6, 2021), then the Secret Service must send NARA a report within 30 calendar days of the date of this letter with a report documenting the deletion," Brewer wrote in the letter to Damian Kokinda, the DHS Records officer, referencing the DHS Office of Inspector General.

The possible deletion of texts was first brought to light last week by the Homeland Security inspector general, who sent the chairs of the House and Senate Homeland Security committees a letter informing them that the texts may be missing and raising concerns that DHS officials had been slow to respond to their requests for information.

The letter led the House select committee investigating the January 6 insurrection to call the inspector general, Joseph Cuffari, into a closed-door meeting two days after his letter was released. The committee also quickly issued a subpoena Friday to the Secret Service, demanding the records, their first such request of an executive branch agency.

The National Archives request is separate and apart from the House's January 6 investigation. Their mission is to protect and preserve government records and by statute can compel an agency to explain why records may have gone missing. The probe into what went wrong will not be conducted by the Archives itself, but instead by Secret Service, which must then issue a report back to Archives.

"USSS has 30 days to submit a report to NARA on their investigation into the circumstances of this alleged unauthorized deletion," a spokesperson for the National Archives said in a statement to CNN. "In general, investigations into occurrences of unauthorized disposal, deletion or removal are conducted by the designated Agency Records Officers who direct the records management programs in agencies."

The Department of Homeland Security has previously said that it will comply with the subpoena request by the January 6 committee, saying in a statement that the department "has ensured and will continue to ensure that both the DHS Office of the Inspector General (OIG) and the Select Committee to Investigate the January 6 Attack on the United States Capitol have the information they have requested."

Members of the select committee believe it is possible the text messages could still be recovered. They were planning to receive some of the material as soon as Tuesday.

"We did get a briefing from the inspector of general of Homeland Security," Rep. Zoe Logren, a member of the committee and a Democrat from California, told ABC News on Sunday. "And then there was a statement made by the spokesperson for the department saying that it wasn't true, it wasn't fair, and that they, in fact, had pertinent texts. And we go, fine, if you have them, we need them. And we expect to get them by this Tuesday. So we'll see."

This story and headline have been updated with additional developments Tuesday.

CNN's Jamie Gangel and Marshall Cohen contributed to this report.