Authorities arrested more than a dozen people, seized 10 guns and confiscated "large quantities" of heroin, fentanyl and cocaine in a massive anti-drug operation early Tuesday morning, that saw more than 200 law enforcement officers execute raids across the South Shore and in Boston.

The Randolph Police Department, Drug Enforcement Agency, South Shore Drug Task Force and Norfolk District Attorney's Office went to 19 residences in the sweep, which the DA's office described as the culmination of a six-month investigation.

"This investigation was complex and I commend all agencies that were involved for their professionalism and collaboration in getting these deadly drugs off our streets," said Randolph Police Chief William Pace, whose department was the lead agency in the investigation.

The exact amounts of drugs seized is still unclear; evidence from a variety of spread-out crime scenes is still being processed, the DA's office said.

The names of the defendants, who are currently being processed for arraignment, have not yet been released.

The investigation was spurred by the public safety threat of opioid addiction, officials said in the press release.

Massachusetts had at least 1,465 fatal opioid overdoses last year, with another 514 suspected fatal cases. Norfolk County say 158 fatal overdoses in 2016, DA Michael W. Morrissey said in a statement.

"Law enforcement is pushing hard for increased addiction prevention, treatment for addiction and diminishing the demand for these drugs, but it remains vital that we work to close off the supply of poisons that are killing our citizens by the hundreds," Morrissey said.