America First Policy Institute, which has prepped policy proposals for a hypothetical second Trump administration, discovered the breach last week. The breach affected its computer systems and led to stolen materials from online accounts. The organization did not say specifically what materials were compromised but said its systems have been secured.

The Washington Post reported that federal authorities believe it was done by Chinese hackers.

Marc Lotter, the organization’s chief communications officer, said in a statement that “it is not surprising that hostile foreign actors would attempt to infiltrate our IT.”

“As the leading policy group in the America First movement, it is not surprising that hostile foreign actors would attempt to infiltrate our IT. The tactics, techniques, and procedures of the threat actor are similar to that of nation-state sponsored activities we have seen, allowing us to remediate and respond quickly,” he said.

America First Policy Institute is led by Brooke Rollins, who was Trump’s domestic policy adviser when he was in office. According to the New York Times, Trump has been probing the idea of having her be his chief of staff if he is elected again. Rollins said in a statement that she has “had zero conversations with President Trump or his team about this,” and is focused on getting Trump reelected.

The breach comes after Iranian hackers stole information from Trump’s campaign over the summer and shared it with President Joe Biden’s team in an effort to interfere in the election.

Intelligence officials have recently warned about election interference by foreign actors. On Monday, the Office of the Director of National Intelligence said they “continue to assess that China is not seeking to influence the presidential election,” instead focusing on congressional races regardless of political affiliation.