Top Senate Republicans have pushed the Biden administration’s top border official to explain how federal law enforcement allowed eight suspected ISIS terrorists into the United States at the U.S.-Mexico border.

Sen. Lindsey Graham (R-SC), the top Republican on the Senate Judiciary Committee, and Sen. Rand Paul (R-KY), the top GOP member on the Senate Homeland Security and Governmental Affairs Committee, announced on Monday that they had contacted Homeland Security Secretary Alejandro Mayorkas and demanded an explanation for how the department screened and vetted eight Russian citizens from Tajikistan.