A U.S. congresswoman is working to verify a document showing that despite agency denials, Customs and Border Protection agents were ordered to detain Iranian-American travelers at the U.S.-Canada border in Washington state early this month.

U.S. Rep. Pramila Jayapal said Thursday that up to 200 travelers with links to Iran were detained for as long as 12 hours as they crossed the border from Canada into Washington state the weekend of Jan. 5-6, following a U.S. drone strike that killed a top Iranian general.

CBP initially denied targeting travelers based on national origin, but the document obtained by a local immigration attorney appears to show otherwise.