Don’t know about the source, but I’ve read articles on FR that have said that Muslim prayer rugs were found on the border and that Border Agents have said that middle easterners were crossing or trying to cross.
Wouldn’t be surprised on either one.
I am in TX. Folks from my Church that have a ranch on the border near Del Rio, have found prayer rugs and Qurans on their place.
The first time was back in about 2003, IIRC