The leaders of the House Oversight Committee raised concerns about how President Donald Trump’s use of Twitter complies with federal records laws, and they questioned government employees’ use of encrypted messaging applications.

In a letter to the White House, Committee Chairman Jason Chaffetz (R-Utah) and the panel’s top Democrat, Elijah Cummings (Md.), said that many tweets coming from Trump’s two Twitter accounts — his @POTUS presidential account and his personal @realDonaldTrump one — constitute communications that would have to be preserved under the 1978 Presidential Records Act.

According to the letter, the law requires that government employees, including the president and vice president, provide a record of official communications conducted on personal or government email within 20 days.

The lawmakers said that if Trump has deleted tweets that aren’t archived then it could be a violation of the 1978 law. The pair cited a Feb. 21 article from The Independent about a deleted tweet that read: “Meeting with Generals at Mar-a-Lago in Florida. Very interesting!”

Chaffetz and Cummings also said federal employees’ reported use of encrypted messaging apps such as Confide or WhatsApp could “result in the creation of presidential or federal records that would be unlikely or impossible to preserve.” They said that while encryption can protect against cyberattacks, digital security “does not justify circumventing requirements established by federal recordkeeping and transparency laws.”

The letter cites a Feb. 2 article published by Politico saying federal employees are using encrypted apps such as WhatsApp and Signal to communicate with other government workers and to contact members of the press, as well as a Feb. 8 Axios story about members of the Trump administration using Confide, an encrypted messaging app that deletes messages after they’ve been read.

The Oversight Committee leaders requested that Donald McGahn, the counsel to the president, identify any senior officials who have used an alias email account since Jan. 20 and provide details about policies related to creating presidential records on electronic messaging.

Chaffetz and Cummings sent a similar letter on Wednesday to 55 federal agencies requesting information on policies and training procedures regarding the Federal Records Act.

The White House did not respond to request for comment.