As staff for the Senate Intelligence Committee gathered information to conduct oversight of the CIA, the CIA was secretly monitoring them, according to reports from McClatchy [News] and the New York Times. The committee staff was reviewing documents in a secure room at CIA headquarters as part of its investigation into the CIA's now-defunct detention and interrogation program, but the agency was secretly monitoring their work, according to reports. Complaints about the spying have reportedly prompted the CIA inspector general -- the agency's internal watchdog -- to look into the agency's behavior. Sen. Mark Udall, D-Colo., seemed to reference the surveillance in a letter to President Obama ... in which he urged the president to support the fullest declassification of the committee's CIA report. As you are aware, the C.I.A. has recently taken unprecedented action against the committee in relation to the internal C.I.A. review, and I find these actions to be incredibly troubling for the committee's oversight responsibilities and for our democracy," Udall wrote. "It is essential that the Committee be able to do its oversight work -- consistent with our constitutional principle of the separation of powers -- without the CIA posing impediments or obstacles as it is today." Sen. Martin Heinrich, D-N.M., another member of the intelligence committee, declared in a statement Wednesday, "The Senate Intelligence Committee oversees the CIA, not the other way around."