The U.S. Postal Service is struggling to catch packages of fentanyl delivered from overseas by mail, NPR reports.

The Postal Services receives about 1.3 million packages a day from overseas, but only inspects about 100, according to former Department of Homeland Security official Juliette Kayyem.

In the six months from October 2017 through March of this year, 934 pounds of narcotics were seized—almost as much as were captured in the previous 12 months, according to U.S. Customs and Border Protection (CPB). This is just a small fraction of what is believed to be arriving in the United States.

Senator Rob Portman of Ohio is sponsoring the STOP Act, which would require mailers of international packages to provide data, including the contents of packages, at the sending post office. That information would be entered in a database available to U.S. authorities, and could help CPB screen packages.