The United States Secret Service is a lot like indoor plumbing: It’s something you only think about when there is a problem. While the federal law enforcement agency does have a role investigating financial crimes like counterfeiting, it’s best known for its role protecting members of the executive branch, like the president and vice president and their families.

In this capacity, they are often part of the background. They’re the people in dark suits and earpieces who are always very near the president but ideally just outside the frame. When they come into focus, it’s a sign that something has gone wrong. And things have gone very wrong for the Secret Service lately, as text messages sent by agents during the January 6 attack on the Capitol appear to have been erased.

Last week, the inspector general for the Department of Homeland Security, under which the Secret Service operates, sent a letter to Congress informing them that text messages sent by agents on and before January 6 had been erased. A spokesperson for the Secret Service claimed that this was part of a long-planned “system migration,” but the erasures have now spurred a criminal investigation after investigators could find only a single relevant text message from two dozen agents subject to a congressional subpoena.

Further concerns were raised after the Washington Post reported that the DHS inspector general had known about the erased messages since February but had not said anything.

This prompted a joint statement on Wednesday from Reps. Bennie Thompson (D-MS) and Liz Cheney (R-WY), the chair and vice chair of the House’s January 6 committee:

We have concerns about a system migration that we have been told resulted in the erasure of Secret Service cell phone data. The U.S. Secret Service system migration process went forward on January 27, 2021, just three weeks after the attack on the Capitol in which the Vice President of the United States while under the protection of the Secret Service, was steps from a violent mob hunting for him. Four House committees had already sought these critical records from the Department of Homeland Security before the records were apparently lost. Additionally, the procedure for preserving content prior to this purge appears to have been contrary to federal records retention requirements and may represent a possible violation of the Federal Records Act.

The text messages have become increasingly vital after the testimony of former White House aide Cassidy Hutchinson, who recounted an astonishing scene where former President Donald Trump attempted to wrest control of a Secret Service vehicle in order to join the crowd at the Capitol on January 6. Hutchinson relayed a story as it was told to her by Tony Ornato, a top White House aide on detail from the Secret Service, and Bobby Engel, the head of Trump’s security detail.

As Hutchinson related it in a June public hearing, Trump became enraged when agents tried to take him back to the White House and not to the Capitol. “I’m the f-ing president, take me up to the Capitol now,” Trump reportedly exclaimed before reaching for the steering wheel of the Secret Service vehicle. He then “lunged at [the] clavicle” of an agent trying to restrain him, Hutchinson said.

Immediately after her testimony, anonymous Secret Service agents told several outlets that Ornato and Engel are prepared to deny that this happened, but neither has testified about it under oath. In its hearing on Thursday, the committee said other anonymous sources had corroborated what Hutchinson said.

Visibility into the text messages between agents would confirm what happened and could further prove Trump’s intent to join the crowd at the Capitol in its effort to halt the certification of the 2020 presidential election. They also might offer more details on what Trump was doing during the attack. The committee established in Thursday’s hearing that Trump spent most of the time during the attack watching Fox News and lobbying senators to back his efforts to overturn the 2020 elections.

In addition, they could clarify what was happening around Vice President Mike Pence that day. The hearing Thursday displayed audio transcripts of Secret Service agents at the Capitol who worried that Pence might not be able to escape to a secure location in the Capitol, and one anonymous security official testified that members of Pence’s detail were so concerned that they called family members to say goodbye in case they did not survive.

Afterward, when Pence fled, he refused the requests of agents to get into a car because he didn’t trust them not to drive away and evacuate him from the Capitol. Pence, who thought it was important for the country to proceed with finishing the task Congress started that day, didn’t want to prevent the election’s certification if he couldn’t return to the Capitol that night, as the Washington Post’s Carol Leonnig and Philip Rucker reported in their book I Alone Can Fix It. Pence told Tim Giebels, the head of his detail, “I’m not getting in the car, Tim. I trust you, Tim, but you’re not driving the car. If I get in that vehicle, you guys are taking off. I’m not getting in the car.”

At the same time, Ornato told Keith Kellogg, Pence’s national security adviser, that there were plans to move the vice president to Andrews Air Force Base. Kellogg replied, according to the Post, “You can’t do that, Tony. Leave him where he’s at. He’s got a job to do. I know you guys too well. You’ll fly him to Alaska if you have a chance. Don’t do it.”

The missing text messages might reveal more details about this as well, but it is unclear if we will ever see them. The Secret Service says it’s unlikely they can be recovered. We may, though, learn more over the course of the criminal investigation about who erased them and why.

In the meantime, committee member Rep. Zoe Lofgren (D-CA) told reporters on Thursday night that both Ornato and Engel have retained private lawyers.