Rioting Darwin detainees start fire

Accused Indonesian people smugglers have set mattresses on fire in an open area at a Darwin immigration detention centre, but the protest action caused no lasting damage, authorities say.

Department of Immigration spokesman Sandi Logan says the protesters were all Indonesian crewmen facing people-smuggling charges, but it was not clear what had triggered the riot.

The protest started at 4am (6.30am NZT) on Sunday when two Indonesian crewmen climbed a tree and refused to get down, Mr Logan said.

Other detainees joined in, yelling and starting a fire in the yard at about 7.30am, he said.

The fire caused a huge plume of black smoke to rise above Darwin's outskirts.

He said firefighters had extinguished the blaze by 8am.

"It's not clear at this stage what their grievances are," he told Sky News.

"Some of the protesters had gathered together refuse, paper and a couple of mattresses and thrown them into a pile out in the open compound area and lit that.

"(The smoke) looked quite spectacular ... but, in fact, it has caused no building or structural damage.

"These sorts of actions will not benefit the detainees inside the detention centre."

Some protesters climbed onto a rooftop and brandished poles during the protest but they had returned to their rooms, Mr Logan said.

He said the protest would not impact on ongoing police investigations and people smuggling prosecutions going through the courts.

"The next step will be to study CCTV vision, take statements from those who witnessed what occurred and for the NT police to determine whether charges will be laid," Mr Logan said.

The detention centre at the Coonawarra Naval Base houses 500 detainees, including 150 alleged Indonesian people smugglers.

Immigration department officials cannot confirm how many detainees were involved in the protest but believe it could be up to 97 -- the total number of Indonesian crewman detained in the compound.

NT police officers were at the centre, but the force declined to comment.

- AAP