A spokeswoman for the presidency of El Salvador, Wendy Ramos, did not respond to requests for information about Senator Van Hollen’s meeting with Abrego Garcia, including whether he had been returned to the prison where American officials have said he is being held, the Terrorism Confinement Center, or CECOT.

Van Hollen, 66, got his start in politics as a staffer for former Maryland U.S. Sen. Charles Mathias in the 1980s, going on to staff the Senate Foreign Relations Committee and, later, Maryland Gov. William Donald Schaefer.