The ranking member of the Senate Homeland Security and Governmental Affairs Committee is demanding that U.S. Immigration and Customs Enforcement explain why it has purchased commercial spyware capable of covertly taking control of phones as well as collecting messages, photographs, location information and other personal data.

Democratic Sen. Gary Peters of Michigan called the purchase “one of the most significant expansions of DHS and ICE’s surveillance ambitions to date,” flagging potential civil liberties concerns and risks to U.S. national security. Peters sought clarity from Homeland Security Secretary Markwayne Mullin in a letter exclusively obtained by CBS News and dated July 23, calling into question ICE’s $2 million, sole-source purchase of Graphite, a surveillance tool developed by Paragon Solutions and now owned by REDLattice.

“Misuse of Graphite is not hypothetical,” Peters wrote, mentioning public reporting that more than 90 journalists and civil society members were targeted by the technology across several countries.