The St. Tammany Parish Sheriff’s Office has booked another eight suspects in a yearlong heroin trafficking investigation in western St. Tammany and Tangipahoa parishes.

Last week, the Sheriff’s Office said 15 people had been arrested, including 29-year-old Scottie Fisher, whom Sheriff Jack Strain described as the head of a distribution ring that at its height moved half a kilogram of heroin a month.

A dozen other suspects were still being sought at the time, but now, all but four have been booked.

Those still at large are Brandon Spear, 27; Androne James, 31; Pierre James Jr., 29; and Damien James, 27.

A number of suspects have turned themselves in to authorities: Steven Jeffery Korte, 29, booked Thursday on racketeering; Ryan Adams, 27, booked Tuesday on attempt and conspiracy to distribute a Schedule I narcotic; Paul Jonathan Jarrett Doty, booked Monday on attempt and conspiracy; Ladameyar Fisher, booked Wednesday on racketeering; and Pierre Warford, 24, booked Wednesday on attempt and conspiracy.

In addition, Robert Williams Jr., 24, was picked up Wednesday and booked on racketeering, and Melvin Lacrouts III, 28, and Mark Mahoney, 32, were arrested on Monday and Tuesday, respectively, and booked on attempt and conspiracy.

The investigation was carried out by a task force made up of detectives with the St. Tammany Parish Sheriff’s Office and the Covington and Mandeville police departments. The group also enlisted the help of State Police, the Tangipahoa Parish Sheriff’s Office, the U.S. Department of Homeland Security, U.S. Customs and Border Protection, and the U.S. Drug Enforcement Administration.

Follow Sara Pagones on Twitter, @spagonesadvocat.