Two top Democrats on the Senate Homeland Security and Governmental Affairs Committee are worried that President Trump’s smartphone use is a risk to national security.

“Public reports originally indicated that President Trump began using a ‘secure, encrypted device approved by the U.S. Secret Service’ prior to taking office. Subsequent reports, however, suggest that President Trump may still be using his personal smartphone, an ‘old, unsecured Android phone,'” Sens. Claire McCaskill of Missouri and Tom Carper of Delaware wrote Defense Secretary Jim Mattis in a letter made public Monday.