Some 21 adults and a 15-year-old boy were arrested last week in connection with a heroin-trafficking ring in Middlesex and Somerset counties.

The roundup followed a six-month investigation by the Somerset County Organized Crime and Narcotics Task Force and the Middlesex County Gangs, Guns and Drugs Task Force; authorities in both counties arrested the suspects at their homes, according to an announcement from Middlesex County Prosecutor Bruce J. Kaplan and Somerset County Prosecutor Wayne J. Forrest.

Police seized more than 600 bricks of heroin, with a total street value of $400,000 to $450,000. Each brick contains 50 bags of heroin packaged for street distribution. Officials said the total weight of the seized heroin was approximately 3 kilos, or 6.6 pounds. Authorities also confiscated smaller amounts of cocaine and marijuana, as well as two handguns, ammunition, six automobiles and more than $40,000 cash.

The arrests were made between March 26 and 29. Suspects were arrested on charges including counts of conspiracy, possession and distribution of heroin. Bails range from $10,000 to $750,000 for the eight suspects who are being held at the Middlesex County Adult Correction Center in North Brunswick. Thirteen of the adults and the juvenile were released on their own recognizance.

Johnel Dunlap, 38, of Elizabeth, was charged with being the leader of the heroin network, as well as conspiring to distribute heroin, and possession with intent to distribute more than 5 ounces of heroin. He was held on $750,000 bail.

Also arrested on charges of conspiracy, possession and possession with intent to distribute were William Newbill, 30, of Elizabeth, and Joseph Mosley, 26, of New Brunswick. Their bails were set at $250,000 each. Tehron Luster, 35, of New Brunswick, was charged with conspiring to distribute cocaine, possession of cocaine and possession with intent to distribute it. His bail also was set at $250,000.

In addition, Jose R. Maldonado, 28, of the Somerset section of Franklin Township, Richard Daggett, 31, of the Parlin section of Sayreville, and Katiria Gomez, 27, of East Brunswick, were charged with conspiring to distribute a controlled dangerous substance. Bail was set at $25,000 for Maldonado and Daggett. Gomez’s bail was set at $10,000.

Arrested on charges of possession and possession with intent to distribute less than one-half ounce of heroin were Wilkins Gonzalez, 33, Naykeeya Willard, 31, and Lashawn Higgins, 23, all of New Brunswick. Bail was set at $100,000 for Gonzalez. Willard and Higgins were released on their own recognizance.

The 15-year-old was charged as a juvenile with possession and possession with intent to distribute heroin.

The other 11 suspects — from Sterling, Piscataway, Hillsdale, South Amboy, Woodbridge, East Brunswick, Franklin Township, Parlin and Keyport — were charged with conspiracy to possess and attempt to possess a controlled dangerous substance. All were released on their own recognizance.

Authorities said the investigation is continuing and additional charges are anticipated.

The two prosecutors’ offices received assistance from the Sayreville, East Brunswick, New Brunswick and Franklin Township police departments, as well as members of the State Police and the Union County Prosecutor’s Office,