NBC News Pete Williams and Julia Ainsley are reporting that the inspector general's investigation into the Department of Homeland Security over the missing text messages from Jan. 5 and 6, 2021, has now become a criminal probe. The results of what unfolded could also be referred to federal prosecutors for indictment.

"The DHS Inspector General informed the Secret Service on Wednesday evening that the investigation is now criminal and that it should halt all internal investigations on the missing text messages," a letter relayed to reporters says.

"To ensure the integrity of our investigation, the USSS must not engage in any further investigative activities regarding the collection and preservation of the evidence referenced above,” DHS Deputy Inspector General Gladys Ayala wrote in the letter. “This includes immediately refraining from interviewing potential witnesses, collecting devices or taking any other action that would interfere with an ongoing criminal investigation.”

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The letter was sent to Secret Service Director James Murray, but Murray is about to leave the Secret Service to take a job at Snapchat, the social media site that, ironically, allows message senders to erase them after being viewed.

The Secret Service said in a statement that they got the letter and have informed the House Select Committee investigating the Jan. 6 attack on Congress of the probe.

Earlier on Thursday, DHS told the Secret Service to stop its internal inquiry, which could cause some debate.

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