Lawmakers have written to U.S. President Joe Biden and Treasury Secretary Janet Yellen requesting information on the extent to which Hamas is using cryptocurrency to raise funds. The letter cites concerns raised by recent reporting and blog posts from crypto analytics firms, but notes that the scale of the problem is unclear. The lawmakers have called for a better understanding of the size and scope of Hamas's digital asset operations, as well as the success of U.S. efforts to seize illicit digital assets. The letter was signed by over 50 House representatives, mostly Republicans, and comes ahead of a hearing on illicit activity in digital assets.