About 11.30am on April 30, a number of inmates allegedly caused significant damage to the correctional centre and were on the roof of the premises.

No police response was requested at the time.

Officers from Hunter Valley Police District commenced an investigation in May.

Following extensive inquiries, police issued Court Attendance Notices (CAN) to 21 men - aged 22 to 39 - for the offences of riot and participate in criminal group.

Nine of these men were served a CAN at a Goulburn prison, and six were served at a correctional facility at Cessnock.

A 24-year-old man was issued at CAN at a correctional facility at Kempsey, and a 28-year-old man was served at a Wellington jail.

A 33-year-old man was issued a CAN at a home in Hamilton South, and a 32-year-old man was served at a home in Gosford.

These 19 men are due to appear at Cessnock Local Court on Thursday.

A 32-year-old man was arrested at Surry Hills Police Station and served a CAN on Wednesday. He was refused bail to appear at Central Local Court on Thursday.

A 39-year-old man was arrested at a home in Tamworth and served a CAN earlier this month. He was refused bail and appeared at Tamworth Local Court on July 3, when he was granted conditional bail to next appear at the same court on August 24.

Police will allege that the men threatened unlawful violence towards Corrective Services NSW staff and damaged several areas of the facility, including the ceiling, doors and roof, along with items inside. The damage is estimated to be valued at more than $130,000.

Police have worked closely with Corrective Services NSW Special Operational Group North staff and officers during this investigation.