According to a story in the Daily Dot [dailydot.com], the Office of Inspector General of the US Department of Justice [wikipedia.org] (DOJ-OIG) is looking into the use of telephone metadata (call detail records [wikipedia.org]) collected in bulk by the NSA (under its interpretation of Section 215 [eff.org] of the USA PATRIOT Act). The DOJ-OIG is also checking into possible use of parallel construction at the DEA, which was alleged in 2013 by anonymous sources [reuters.com].
Parallel construction is false testimony about how evidence or investigative leads were obtained. It is used to make it falsely appear that evidence is admissible in court, or to conceal the origin of the information.