Federal officials on Thursday announced the indictment of 20 people charged with participation in a cocaine ring that had supplied Dorchester, Mattapan and Jamaica Plain for more than 20 years.

At the center of the ring, the US Attorney's office in Boston charged, was Michael Williams, 43, who used three deckers at 132 and 136 Greenwood St. and a small vacant lot at 138 Greenwood St. and a single-family home at 8 Peacevale Rd. to store, prepare and distribute cocaine products.

Federal agents moved to seize the properties and said they also conducted raids on locations in Jamaica Plain, Quincy and Brockton.

In addition to Williams, those arrested include Donald Williams, 33, and Noel Williams, 54, of Dorchester. Also: Dwayne Person, 40, Dennis Person, Kevin Pena, 24, Anastacio Lopez, 34, Eydris Adams, 34, Nicole Moore, 33, Beverly Perons, 39, Jerome Marion, 33, George Leary, 60, Ramon Lomax, 45, Anthony Madden, 49, Shawn Walker, 35, Debra Brown, 50 and Frank Copelnad, 45, all of Dorchester.

They are charged with one count of conspiracy to possess with intent to distribute and distribution of more than 500 grams of cocaine and more than 280 grams of cocaine base.

Convictions would carry minimum sentences of 10 years to life, lifetime supervision after release and up to a $4 million fine each.