Labor is demanding Immigration Minister Scott Morrison give a full explanation about what he knew about a riot on Manus Island, after backtracking on claims a death occurred outside Australia's detention centre.

Mr Morrison now says most of the "riotous behaviour" that resulted in the death of an Iranian man and left 62 other asylum seekers injured happened inside the Papua New Guinea facility.

"The further information I have now received casts further doubt on the initial advice that his injuries were sustained outside the centre," he said in a statement issued just before 9pm on Saturday.

Mr Morrison also raised questions about G4S, the security firm which runs the centre housing 1300 asylum seekers.