The NSW government has asked for an urgent review after a 21-hour riot at a juvenile justice centre on the state's Central Coast.
The riot - in which inmates used makeshift weapons to "target sex offenders" - came to a peaceful end on Monday evening as police warned the rioters would face court.
The "sudden and unprovoked" riot broke out at the Frank Baxter Juvenile Justice Centre at Kariong on NSW's Central Coast at about 8.30pm on Sunday, NSW Police said.
Officers were called to the location following reports that a number of detainees had assaulted other juvenile residents.
The 21 hour-long riot came to an end at 5.30pm on Monday following "highly successful negotiation", police said.
Twenty males, aged between 16 and 20, have been arrested.
Seven detainees were injured during the incident, with one 18-year-old receiving treatment for stab wounds and facial injuries at Gosford Hospital. He remains in intensive care in a critical condition.
Throughout Monday nine detainees surrendered peacefully to police until officers from the Tactical Operations Unit and the Public Order and Riot Squad gained access to the roof of the facility - where the remaining rioters had gathered - and arrested the remaining detainees peacefully.
In a press conference on Monday evening, a police spokesman said anybody involved with the riot would be charged with the offence of rioting, which carries a 15-year sentence.
"It is important, ladies and gentlemen, that the detainees understand that there will be consequences for their actions," he said.
NSW Minister for Families and Communities Gareth Ward said he had called for an urgent independent review into the incident to "get to the bottom of what happened". The review will be conducted by former Police Assistant Commissioner Lee Shearer.
"The incident at Frank Baxter Youth Justice Centre is unacceptable and we are treating it very seriously. I commend NSW Police for resolving the situation," he said.
"Our priority is the safety and wellbeing of staff and detainees involved the incident."
The union which represents prison guards said the offenders stole keys from an officer to obtain garden tools including a hedge trimmer and shovels from a maintenance shed.
Public Service Association general secretary Stewart Little described the riot as "nothing short of horrific".
Urgent review into NSW prison riot
In a statement early on Tuesday, police said three men continued to receive treatment at Gosford Hospital.
They included a man with stab wounds and a collapsed lung, another with head and face injuries and a third man with a broken ankle.
Police were in the process of charging 21 people with a riot - five adults and 16 youths.
The adults were due to face the Gosford Local Court on Tuesday while the youths would appear in the Woy Woy Children's Court.
Families, Communities and Disability Services Minister Gareth Ward said the incident was unacceptable and the state government was treating it seriously.
Mr Ward said he has asked for an urgent independent review into the incident, to be conducted by former assistant police commissioner Lee Shearer.
"This inquiry will get to the bottom of what happened at Frank Baxter," Mr Ward said in a statement on Monday.
