Deleted Secret Service texts sent on January 6, the day of the insurrection at the US Capitol, and the day before will be released by Tuesday to the House committee investigating the failed attempt by supporters of Donald Trump to overturn the 2020 presidential election result, a panel member said.

“You can imagine how shocked we were to get the letter from the [Department of Homeland Security] inspector general saying that he had been trying to get this information and that they had, in fact, been deleted after he’d asked for them,” committee member and California Democratic congresswoman Zoe Lofgren told ABC’s This Week.

“We need all the texts to get the full picture,” Lofgren added.

The Secret Service’s account about how text messages from the day before and the day of the Capitol attack were erased has shifted several times, the inspector general for the Department of Homeland Security told the House January 6 select committee at a briefing on Friday.

At one point, the explanation from the Secret Service for the lost texts was because of software upgrades, the inspector general told the panel, while at another point, the explanation was because of device replacements.

The inspector general also said that though the Secret Service opted to have his office do a review of the agency’s response to the Capitol attack in lieu of conducting after-action reports, it then stonewalled the review by slow-walking production of materials.

After the inspector general raised his complaints, he then discussed the feasibility of reconstructing the texts. But the issues so alarmed the select committee that the panel moved hours later to subpoena the Secret Service, according to participants at the briefing.

The string of fast-paced developments on Capitol Hill reflected how the erasure of the text messages – first disclosed in a letter to Congress by the inspector general, Joseph Cuffari – has become a top priority for the congressional inquiry into January 6.

The circumstances surrounding the erasure of the Secret Service texts from the day before and the day of the Capitol attack have become central for the select committee as it investigates how it planned to move Donald Trump and Mike Pence as the violence unfolded.

The texts are potentially significant for investigators as the Secret Service played a crucial role in preventing Donald Trump from going to the Capitol that day and wanted to remove then-vice-president Mike Pence from the complex, according to the panel.

In the letter, the inspector general said that certain Secret Service texts from 5 January and 6 January 2021 were erased amid a “device replacement program” even after he had requested the messages for his internal inquiry.

The Secret Service has disputed that, saying in a statement that data on some phones were lost as part of a pre-planned “system migration” in January 2021, and that Cuffari’s initial request for communications came weeks later in late February 2021.

But the select committee questioned the Secret Service’s emphasis on that date, the participants said, and noted in the subpoena letter that the request for electronic communications in fact first came from Congress, ten days after the Capitol attack.

The congressional request from 16 January 2021 addressed to multiple executive branch agencies – including the Homeland Security Department, which oversees the Secret Service – was for all materials referring or relating to the riot.

Members on the select committee were privately skeptical of the notion that the Secret Service managed to inadvertently erase key messages during a 10-day period that was among perhaps the most tumultuous for the agency, the participants said.

If some of the texts were deliberately erased after the 16 January 2021 request, that could amount to obstruction of a congressional investigation, one of the select committee’s members added on Friday.

A spokesperson for the Secret Service could not immediately be reached for comment.

The select committee has spent recent days trying to establish whether it was all texts from 5 January and 6 January 2021 that were lost or just some, exactly how the texts came to be erased, and whether additional days’ worth of texts from that month were missing.

The participants at the briefing said Cuffari was not able to provide clear answers on those questions, beyond the fact that he understood a proportion of texts from both the day before, and the day of, the Capitol attack remain unaccounted for.

The unanswered questions were because of a lack of transparency from the Secret Service, the participants said Cuffari indicated. At the briefing, Cuffari said the explanation for the lost texts shifted from software upgrades to device upgrades to still other issues.

Cuffari also expressed optimism to the select committee that the erased texts could be reconstructed through previous back-ups of messages or tools available to federal law enforcement, the participants said.

The justice department inspector general has previously been able to retrieve lost texts, using “forensic tools” in 2018 to recover messages from two senior FBI officials who investigated former presidential nominee Hillary Clinton and Trump and exchanged notes criticizing the latter.

The controversy over the erased Secret Service texts erupted on Wednesday after Cuffari’s letter became public, and the select committee went into overdrive to assess the impact on its investigation.

That prompted the select committee chairman Bennie Thompson to discuss the matter with the panel’s staff director, David Buckley, and his deputy, Kristin Amerling, and later with the full select committee, which asked Cuffari to provide a closed-door briefing.