The Central Intelligence Agency is denying claims that some of its agents spied on high level lawmakers.
For four years, staffers for the Senate Intelligence Committee investigated a top secret CIA program aimed at pushing terror suspects to the breaking point.
Now lawmakers say the agency was monitoring their investigation, violating the constitutional principle of separation of powers.
CIA agents reportedly searched the computers of committee staff members in an attempt to learn how they gained access to the CIA's own 2009 review of their interrogation program.
The situation has many senators crying foul.
"The CIA has recently taken unprecedented action against the committee." Sen. Mark Udall, D-N.M., wrote in a letter to President Barack Obama.
Senate Armed Services Committee Chairman Carl Levin, D-Mich., said that if true, it's "an extremely serious matter" that could "violate federal law."
Even former members of the CIA said they were troubled by the reports.
"The CIA, it's a red line. It should not be looking into the Senate or any other government agency. It's a foreign intelligence operation meant to spy on foreign countries, not our own government," former CIA officer Bob Baer said.
But the CIA is pushing back.
Some agency officials have implied that it's actually the committee staffers that acted out of line, penetrating parts of the CIA's computer network they weren't authorized to access.
"I am deeply dismayed some members of the Senate have decided to make spurious allegations about CIA actions that are wholly unsupported by the facts," CIA Director John Brennan said.
Brennan said he's confident authorities will determine where wrongdoing, if any, actually took place.