Official at the Australian Immigration and Border Protection department said that the Papua New Guinean authorities are investigating the death.
The BBC reported that PNG Police are treating the death as suicide, however, other inmates have expressed doubts.
Though the man has not been identified as of yet, he is said to be an Iranian national.
The detention centre, which has coped up controversy and condemnation from human rights groups, due to lack of hygiene and inadequate facilities, is due to close by Oct 31, later this year.
Image: flickr: DIAC images/Wikipedia