A U.S. customs official admitted "enormous mistakes" were made when agents subjected dozens of people of Iranian descent to long questioning last month at the Blaine border crossing, according to two congress members.

“It was extremely gratifying for the first time to hear from CBP that in fact something very serious went wrong that weekend, there were enormous mistakes made,” said Rep. Pramila Jayapal of Seattle.

Jayapal and Rep. Susan Del Bene met Monday with Adele Fasano, head of U.S. Customs and Border Protection in Seattle.

They said Fasano expressed deep concerns about what happened and wants to get to the bottom of it.

The agency originally denied that it detained people of Iranian descent at the Peace Arch on January 4-5. The detentions came shortly after a U.S. drone strike in Iraq that killed a top Iranian general.

Instead, the agency said there were delays of up to four hours because of holiday staffing issues, and it said people were not being targeted because of their nationality.