Amid the backlash to the Trump administration’s use of the private messaging app Signal for sensitive U.S. military planning in Yemen, Politico reported Wednesday that national security adviser Mike Waltz’s team set up at least 20 such chats.

The people used the group chats to discuss issues related to China, Ukraine and Europe, Gaza and the Middle East, along with other regions, according to Politico.

The outlet cited four people who were “personally added” to the Signal chats; they all said that sensitive information had been discussed there. As one individual told Politico, “Waltz built the entire NSC communications process on Signal.”

The claim comes on the heels of a Washington Post report stating that Waltz and other White House security officials have been using their personal Gmail accounts to discuss government business.

How the White House uses Signal became a topic of national debate last month when The Atlantic’s editor-in-chief, Jeffrey Goldberg, published a bombshell report detailing how he had been accidentally added to a group Signal chat coordinating an airstrike in Yemen. Goldberg then published the texts he received, showing how they contained specific information that could have imperiled the military operation if it had fallen into the wrong hands.

The White House has repeatedly pushed back on concerns about its handling of military plans, with Trump publicly supporting Waltz through the controversy. Officials have said the Atlantic story was a hoax, or overblown, or even irrelevant because the airstrike had been a success.

Bipartisan critics, however, have said that platforms like Gmail and Signal put government secrets at risk of discovery. The Washington Post reported that officials’ Gmail conversations included details of “sensitive military positions and powerful weapons systems relating to an ongoing conflict,” without naming the conflict.

Some government officials have been using Signal for simple coordination, such as setting up a meeting between department heads. But classified or otherwise sensitive information is not supposed to be shared there, and the government already has its own methods of securely conveying information.

Use of Signal and personal Gmail accounts may also violate federal record-keeping regulations that stipulate official communications must be preserved. A publich watchdog group has filed a lawsuit against the Trump administration officials in the Yemen signal chat, accusing them of violating their duty to preserve communications.