SYDNEY - Police investigating a riot at an Australian immigration detention centre were on Friday questioning 22 people about the protests started by asylum seekers whose visa applications had been rejected.

A handful of protesters remained camped out on rooftops at Sydney's Villawood Detention Centre on Friday, with officials sending up supplies of food and water, an immigration department spokeswoman said on customary condition of anonymity.

Around 100 people at the facility were involved in the riot, which began Wednesday night when two detainees climbed onto a roof. Protesters set an oxygen cylinder alight, which led to an explosion, and fire destroyed nine buildings. No one was injured.

Police removed 22 people from Villawood and transferred them to a correctional centre, the immigration department spokeswoman said. They were being questioned by police on Friday.

Acting Prime Minister Wayne Swan said the detainees who were removed are suspected of causing damage during the protest.

"This sort of behavior is absolutely unacceptable," Swan told reporters in Cairns. "They will certainly feel the full force of the law."

Around 400 people are held at Villawood. Many of them are asylum seekers, but the facility also houses people who have overstayed their visas. Swan said the protest was led by asylum seekers who had their visa applications rejected.

Australia has seen a surge of asylum seekers fleeing Sri Lanka, Iraq and Afghanistan, and protests at detention centres have become relatively common. The influx has led to a heated political debate as opposition politicians blame the flow on a relaxation of immigration policies by the ruling Labor Party.