President Donald Trump raised questions Tuesday about the five months of missing messages between two FBI employees who were involved in the Hillary Clinton email investigation.

The FBI agent Peter Strzok and FBI lawyer Lisa Page were found to have previously exchanged emails in 2016 about “an insurance policy” in case Trump won the presidential election. For a time, Strzok served on the team of special counsel Robert Mueller investigating suspicions of collusion between the Trump campaign and Russians.

In a tweet early Tuesday, Trump called this “one of the biggest stories.”

On Friday, the Justice Department provided text messages to congressional committees investigating the department’s conduct during the investigation of Clinton’s private email server.

The committees requested information from two years of communications between Strzok and Page ending last July, when then-FBI Director James Comey he would not recommend prosecution of Clinton, the former secretary of state and 2016 Democratic presidential candidate.

However, text messages between the two were missing from Dec. 14, 2016, to May 17, 2017.

“He thinks that there’s a great cause for concern that five months of text messages have gone missing,” White House press secretary Sarah Huckabee Sanders said during the Tuesday press briefing.

She added that she hopes the media will investigate the matter.

“It looks like there could have been really inappropriate and possibly illegal behavior,” Sanders said.

The Associated Press reported Attorney General Jeff Sessions said Tuesday the Justice Department will “leave no stone unturned to confirm with certainty why these text messages are not now available to be produced and will use every technology available to determine whether the missing messages are recoverable from another source.”

Sessions added, “If any wrongdoing were to be found to have caused this gap, appropriate legal disciplinary action measures will be taken.”

Justice Department official Stephen Boyd sent a letter to congressional committees saying the gap resulted from “misconfiguration issues related to rollouts, provisioning, and software upgrades that conflicted with the FBI’s collection capabilities.” The letter continued, “The result was that data that should have been automatically collected and retained for long-term storage and retrieval was not collected.”