More than 20 inmates have been charged over a riot at Cessnock jail earlier this year - a scene where several prisoners allegedly made their way to the roof and while others are accused of barricading themselves away from staff in an incident that allegedly caused more than $130,000 damage.
The chaos began in the maximum security H Block of Shortland Correctional Centre about 11.30am on April 30.
The situation was under control by about 4pm.
The matter was handled at the time by Corrective Services NSW officers.
NSW Police said in a statement on Thursday morning that Hunter police were not called into the jail for help and their investigation began in May.
They worked with investigators from the Corrective Services NSW Special Operations Group.
Police this week handed court attendance notices to 21 men aged between 22 and 39 for allegedly rioting and participating in a criminal group.
Investigators allege the men threatened unlawful violence against prison officers and damaged parts of the jail including the ceiling, doors, roof and items inside - the value of the damage is estimated to be more that $130,000.
Nineteen of the men are due to face Cessnock Local Court on Thursday.
Nine were charged at Goulburn jail, six at Cessnock jail, one at Kempsey jail and one at Wellington jail.
A 33-year-old man was also served a court attendance notice at a Hamilton South home and a 32-year-old man was issued a notice at a Gosford residence, while a 32-year-old man was charged at Surry Hills and a 39-year-old was charged at Tamworth.
Shortland Correctional Centre holds about 450 prisoners, including murderers and other serious criminals.
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