Along with Nine-Tailed Fox, the main MTF of the game, there are other MTF you can encounter, such as Cloud Nine, or Gamma 5 or Omega 2 or the Mailmen.
WARNING: May contain spoilers about the game.
Cloud Nine Edit
Cloud Nine is a Mobile Task Force squad that shows up at Gate B. If the player deactivates the alpha warheads in the warhead room, a telecom will orders all MTF units to go back and deal with SCP-682, two MTF soldiers, presumably members of Cloud Nine, will come through the door in the control room; and another one in the pathway of Gate B. They will see you, a Class D, and then walk towards and open fire on you, due to the fact that all Class D are active threats. Spoilers end here A document of the MTF units can be found here: