The National Archives and Records Administration informed the White House that it is to keep every tweet sent by President Donald Trump, including those he deletes, according to a letter from the agency sent last week.

The letter comes from David S. Ferriero, the head of the archives, in response to a request for information from Democratic senators Claire McCaskill of Missouri and Tom Carper of Delaware.

Read: Donald Trump Twitter News: President To Continue Tweeting From Personal Account

According to Ferriero, the White House previously agreed to keep a record of all tweets sent by President Trump, including those that the President deletes or corrects.

Ferriero said the National Archives briefed the White House counsel’s office about the archiving law on Feb. 2, but did not say if the agency has been in touch with the Trump administration since then to make sure the policy was being properly carried out.

The Trump White House also has not provided any details as to how exactly it has gone about preserving tweets from the President. During the administration of President Barack Obama, the White House used an automated system that kept copies of each tweet from the President.

Trump has come under fire for his Twitter practices since taking office, including his habit of deleting tweets that contain typos and tweeting a corrected version. He’s done so on multiple occasions, including within minutes of taking office.

On the day of his inauguration, Trump tweeted he was “honered to serve you, the great American people, as your 45th President of the United States." A corrected tweet was later sent before the original was deleted.

Read: Does Twitter Use Show Trump Finally Switched From Unsecured Android?

Senators McCaskill and Carper also asked the National Archives for information about reports that White House staffers were ordered to use smartphone apps that don’t archive emails and communications in order to combat leaked information.

Ferriero said White House guidance “expressly forbids the use of such apps” and noted he wasn’t aware of government officials being instructed to avoid email for communications.

The senators previously raised the issue or preserving communications to and from Trump’s smartphones, including his personal—and unsecured —Android device he recently gave up and his secured iPhone.

The National Archives has not provided any guidance—nor had it received any requests for guidance—regarding preserving communications to and from Trump’s smartphones.