“All the signals of how the senior staff have been put on administrative leave, many of the field staff and headquarters staff have been put on a gag order,” Senator Chris Coons, Democrat of Delaware, who sits on the Senate panels on foreign relations and appropriations, said Saturday afternoon in an interview.

Democrats say the move is illegal without congressional approval.

Nearly 30 career staff in the agency's Legislative and Public Affairs bureau lost access overnight to their emails, the sources said, bringing the total number of senior USAID career staff who have been put on leave over the past week close to 100.