Inmates transferred from the top-security Mecklenburg Correctional Center took advantage of lax conditions at the State Penitentiary in Richmond to plan and launch a riot that left nine guards with stab wounds, according to a report released by a special grand jury in Richmond.

The jury has investigated escapes at the prison and the melee staged April 18 in an unsuccessful attempt to stop the execution of murderer James Briley.

The panel recommended that Corrections Director Allyn Sielaff immediately look to see if all inmates are correctly classified and segregated.

Seven of the 13 inmates indicted in the assault were recently moved to the penitentiary from Mecklenburg.

The panel said the inmates "were known assaultive, antisocial men who, by expert testimony, at no time belonged in a general population setting.

"They went from the close security of Mecklenburg to a general population environment at the penitentiary, affording them the opportunity, freedom and access to weapons to carry forth the attempted murders of that day."

The report classified the attacks as "planned, premeditated and executed with a degree of precision by the group of inmates" and added that there were 18 guards on a hit list.

None of the guards has returned to work. One inmate was also injured in the incident.

Sielaff recently announced a security and management shake-up at the 185-year-old prison designed to improve inmate safety and overall security.