RIOTING asylum seekers have torched buildings inside Sydney's Villawood Detention Centre sparking an explosion as a day-long protest turned violent.
NSW police will investigate after protesting asylum seekers torched nine buildings inside the centre overnight, as authorities struggled to gain control of the volatile situation.
Negotiators are still working to talk down two protesters who remain on the roof of the detention centre.
By daybreak, immigration spokesman Sandi Logan said firefighters had contained the fires and although people remained on the roof, the situation was otherwise in hand.
"We're certainly in the process of regaining control and as daylight comes, we'll be in a much better situation to assess damage," he told ABC Radio.
The asylum seekers still on the roof are reportedly calling for a meeting with the immigration department, but Mr Logan said case managers will continue to be their first point of contact.
"Until they come down, we won't be negotiating, but we are working and managing to get them down from the roof,'' he said.
"We hope that occurs shortly."
Guards had had to "take cover and retreat" during the riots, Mr Logan confirmed, noting that they had not been armed.
He said firefighters had also been attacked with roof tiles, furniture and pieces of wood.
"With daybreak now we're doing an assessment of the damage, we'll have structural engineers and assessors coming," he said.
"We know at least nine structures, including the medical centre, the kitchen, the dining room, the laundry, a computer room and other support amenities were destroyed in the fire overnight," he said.
There will be a police investigation before any charges can be laid.
"NSW Police responded as it's a criminal matter and they've done a wonderful job protecting the firefighters as they've done their job," Mr Logan said.
"There may well be charges laid from this investigation," Mr Logan said.
NSW Police are maintaining a security perimeter outside the centre due to jurisdictional limits, keeping scores of onlookers a safe distance away.
During the drama Australian Federal Police and the centre's security force were trying to move non-protesting detainees to safe areas within the centre.
Fire crews had through the night battled at least three major fires from outside the centre, because detainees were running amok inside the centre.
Ten fire trucks rushed to the facility, in Sydney's southwest, about 10.30pm (AEST) on Wednesday.
Fire Superintendent Chris Jurgeit said three ladder trucks had hoses in elevated positions, dousing a series of buildings, demountables and sheds that were on fire.
"We can't get too much water into the structures," Supt Jurgeit told AAP.
"It's like a prison fire. We don't want to put firefighters at risk."
There were no reports of injuries at this stage.
The problems began on Wednesday morning when two asylum seekers took to the roof of one building reportedly in protest to the department denying their applications.
Refugee Action Coalition's Ian Rintoul said a total of 13 asylum seekers were on the roof by Wednesday evening and were there when others on the ground started the fires.
Mr Rintoul remains in contact with some of the detainees who described the situation as chaotic.
He said the men had been held in detention for 15 months and had their applications rejected twice.
"The two asylum seekers have been rejected at the appeal stage of the determination process and say they do not know what will happen to them now," Mr Rintoul said.
Social Justice Network spokesman Jamal Daoud is also in contact with detainees who said that Serco security officers at Villawood have been attacked.
"The detainees attacked SERCO security with fire extinguishers and (were) throwing objects on them,'' Mr Daoud said in an email.
"The detainees told me that they are experiencing difficult breathing because of this.
"There is total chaos inside the detention (centre), with detainees from the rooftop throwing roof tiles on the ground."