ST. LOUIS (AP) — Two men are accused in a federal indictment of involvement in the killings of two witnesses in drug investigations in St. Louis.

The U.S. Attorney’s office in St. Louis on Thursday announced the indictments of 47-year-old Dionne Gatling and 50-year-old Andre Rush.

The men are accused of involvement in the April 2010 killing of Theodis Howard. Federal prosecutors say Howard was killed as retaliation for being a witness in a drug trafficking case.

They are also accused of roles in the May 2013 killing of Terrance Morgan as part of an effort to keep Morgan from giving investigators information about a drug crime.

Gatling, Rush and two other men are also accused of cocaine and heroin conspiracy charges.

Names of attorneys for the men were not immediately available.