G4S Security was responsible for securing and guarding the detention centre on Manus Island when a violent riot broke out leading to one asylum seeker dying, one being shot and more than 70 injured on Monday night.

On Thursday when Fairfax attempted to view the body of the victim at the basic hospital and morgue on Manus Island, three aggressive G4S security guards refused access and said they had been told to guard the body.

The four guards who were stationed around the rundown air-conditioned freezer shed which is used as a morgue said nobody could see the body without the permission of their superiors. They demanded Fairfax not leave the site until their manager turned up.

The death and the riot are supposedly the subject of separate investigations by the Australian and PNG authorities. However, it appeared no authorities had attempted to inspect the corpse or conduct any form of autopsy.

When Fairfax contacted the local police to ask who was conducting the investigation, they referred all queries to their commander, who they said ''had gone home''.

The G4S guards stationed at the morgue are indicative of the power the security company has begun to wield on the tiny island.

Soon afterwards Fairfax visited the hospital, a G4S bus carrying about eight asylum seekers with distinct injuries arrived for treatment. When Fairfax photographer Nick Moir tried to photograph the bus the G4S guards grabbed him and and confiscated his camera, which was later returned. Local police arrived but refused to intervene and deferred to a PNG G4S manager.

He then insisted on deleting all photographs on Mr Moir's camera.

Meanwhile, an expat worker at the Manus detention centre said relationships between local women and asylum seekers had contributed to tension on the island.

The worker, who asked not to be named, said PNG female staff working in the kitchen would ''disappear'' for up to two hours during night shifts. ''They were running around trying to find friendships,'' he claimed.

Local staff were also understood to be frustrated at the huge pay discrepancies between their salaries and what expat workers were paid. The expat was on a salary of $120,000 a year, while local staff were earning 15 kina a day, the equivalent of about $7.

In the detention centre the PNG Army and PNG's special branch police force were also stationed in the centre. ''The police and the army don't get on. They fight on a regular basis, one wanting to be tougher than the other. There was a lot of acrimony.''But the expat said the PNG ''special branch'' police, who kept weapons on the campsite, typically kept to themselves. ''I found them to be rather silent. They seemed to be observing everything all the time. I have never seen any antagonism,'' he said. ''They were more military-orientated.''

with Sarah Whyte