Seattle area resident Negah Hekmati, one of the Iranian Americans detained and interrogated at the U.S.-Canada border by Customs and Border Protection officials.

The office of Washington Rep. Pramila Jayapal said that a federal civil rights office is opening an investigation into the prolonged detention and interrogation of a number of Iranian Americans and Iranians by Customs and Border Protection officials at the U.S.-Canada border. “This is a critical step toward getting to the truth—and getting real answers about what happened,” she wrote in a tweet.

The Seattle Times reports that the Department of Homeland Security’s Office for Civil Rights and Civil Liberties ”verbally confirmed the investigation Wednesday, and said it is sending investigators to Washington state, according to Subhan Cheema, Jayapal’s spokesman.” It’s still unknown whom or how many people investigators might speak with, but Jayapal said as many 200 people may have been stopped and questioned over the weekend.

The Washington representative had led a group of half a dozen Democratic House chairs demanding more information from the Trump administration on border officials’ actions, writing that CBP’s ongoing denials that there is any order to harass Iranian Americans and Iranians just don’t add up. In a second letter that included the signatures of more than 70 members of the House and Senate, legislators told acting Customs and Border Protection Commissioner Mark Morgan that it’s clear this was a targeted action.

“In conversations with individuals who were held in secondary inspection and community groups representing impacted individuals, it has become clear that this additional screening, holding, and questioning was solely reserved for Iranian Americans,” they said. “State congressional staff members were told that upon their release, a CBP officer told the Iranian Americans they would recommend not traveling for awhile, as they will have to go through this process again, the timing is just bad for them. Iranian Americans were held in secondary inspection for hours, while others were held for shorter time periods.”

“Men, women and children legally entering or returning to the United States at a designated port of entry deserve better than to be arbitrarily held and questioned solely based on their religion, ethnicity, or national origin,” the letter says. In a tweet, Jayapal welcomed the news of the civil rights office investigation. “An important step forward thanks to the courage of those who spoke up to tell their story and our community’s collective ability to quickly draw attention to this. Let’s get answers and make sure it never happens again.”