Complex sentence: Drug Enforcement Agency (DEA) efforts to expose these illegal activities were blocked by Reagan officials; the crack cocaine problem in US inner city neighborhoods exploded, and more aggressive enforcement of federal drug laws led to a dramatic increase in street level arrests for possession.
Split into simpler sentences: Drug Enforcement Agency (DEA) efforts to expose these illegal activities were blocked by Reagan officials, which contributed to an explosion of crack cocaine consumption in US inner city neighborhoods. More aggressive enforcement of federal drug laws resulted in a dramatic increase in street level arrests for possession.