U.S. Attorney David Fein says "Operation Northern Strike" was a 15-month operation that included wiretaps, controlled drug buys and surveillance.
It resulted in a 56-count superseding indictment related to the distribution of crack cocaine, heroin and marijuana in the Hartford area.
Fein says 16 people were arrested during a coordinated roundup this week. He says others were already in custody, and four people were still being sought Thursday.
Authorities say the investigation targeted several small gangs, but not all the defendants are gang members.