Within the United States, the Federal Bureau of Investigation is charged with investigating all crimes involving Powered individuals.  For the most part, this involvement is merely the review of local police investigations, however in other cases the FBI takes a very active role.

The FBI has two sub-divisions which deal specifically with superhumans.  One is the publicly acknowledge para-military group Super-Human Enforcement Legal Liason - S.H.E.L.L. which makes use of highly advanced equipment and training to supplement urban police forces.  The other group is so secret that most of the FBI doesn't know it exists.  Heck, it's so secret that the guys who started forget what D-SAST is supposed to mean.