CTU Phoenix

CTU Denver was a Domestic Unit of the Counter Terrorism Unit. The unit was based Phoenix, Arizona.

Day 3
During Day 3, CTU Phoenix secured a vial of the Cordilla Virus.

AS with CTU Seattle, CTU Las Vegas and CTU Denver, it is assumed that CTU Phoenix found the vial of the virus but no-one actually said that a CTU branch found it and Phoenix was only seen on a screen. Again, Phoenix is quite a large city so it is assumed they would have a Domestic Unit.