The Federal Bureau of Investigation (FBI) is an agency of the United States Department of Justice that serves as both a federal criminal investigative body and an internal intelligence agency (counterintelligence). It has investigative jurisdiction over violations of more than 200 categories of federal crime.
In 1979, following the Three Mile Island incident, FBI squad cars, along with local police and firefighters, arrive at the scene to investigate.
Prior to X-Men: Days of Future Past
In 1989, in partnership with Trask Industries, the FBI unveils a method of using DNA evidence at crime scenes to identify criminals. Off the record, Trask Industries also begins building a private Mutant Registry from this database of DNA, with plans to sell the information to wealthy world governments.
In 2006, the FBI was able to apprehend Mystique. Following her capture, the president and his advisers witness her interrogation by the FBI in the Situation Room via a live video link. During her interrogation, she defiantly refuses to answer questions. Ultimately, she fights with the interrogator, and FBI agents quickly subdue her.
Following the botched interrogation, Mystique is later put under the jurisdiction of the Federal Bureau of Prisons, and is placed in a prison convoy for transfer to a more secure location.