Wilson Security paid at least one Australian security guard to keep quiet about an alleged sexual assault of a local Manus Island worker, in a number of separate payments of up to $15,000 made by the company.

Key points: Wilson Security paid Australian guard to keep quiet about alleged sexual assault of Manus Island worker

Wilson Security paid Australian guard to keep quiet about alleged sexual assault of Manus Island worker One guard was paid $1,500, another allegedly received approximately $15,000

One guard was paid $1,500, another allegedly received approximately $15,000 Four guards were flown off Manus Island before police could investigate

7.30 understands at least one guard, who was present on Manus Island on the evening of the alleged assault and quickly removed from the island the following day on July 16 2015, was paid just over $15,000 by the security company.

The money included the worker's remaining annual leave entitlements and was offered as a non-disclosure payment, meaning the worker could not discuss the incident, nor the work he was doing for the company in the offshore detention centre.

The removal of the workers involved in the alleged rape was considered controversial at the time as local Papua New Guinea police claimed they had not been able to investigate the matter after the local PNG worker had been found naked and disorientated in the men's bathroom on the island in the early hours of the morning.

Another employee of Wilson Security has shown 7.30 a separate Deed of Release they were asked to sign after they left the island, prohibiting them from speaking about Wilson Security, the Australian Border Force or Broadspectrum (formerly known as Transfield).

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In this deed the employee was paid $1,500 for their silence. The money was transferred into the worker's bank account. The deed states that if the worker does break the contract then he or she will be required to pay the money back and that they could face legal ramifications.

Part of the Deed of Release showing the $1,500 payment one guard received from Wilson Security.

It says: "The employee agrees that if approached by anyone, other than law enforcement or authorised government regulatory agency for counsel or assistance in the presentation or prosecution of any disputes, differences, grievances, claims charges or complaints by any third party against the company, Broadspectrum or ABF, the Employee will say no more to the person (whether orally or in writing) in relation to the request other than he cannot provide counsel or assistance to them."

In a statement to 7.30, Wilson Security confirmed it enters into deeds of non-disclosure in matters "that relate to sensitive information or at the conclusion of employment".

They also confirmed a small number of staff had been removed from Manus Island, arguing they were flown off "with the knowledge of the Department of Immigration and Border Protection and the Royal Papua New Guinea Constabulary".

But weeks after the incident Prime Minister Peter O'Neill and local police attempted to extradite the men back to the country so the case could be investigated.

How the night unfolded

The night of July 15 had begun at a bar in the compound where the woman was seen drinking with the workers before the group left to go to their accommodation blocks.

It was here that the alleged assault occurred with at least two of the workers and the female PNG worker.

After the woman was found on July 16, nine expatriate workers were breath tested. 7.30 understands two Wilson guards were still heavily intoxicated and deemed unfit for work.

Within hours, the four men involved in the incident had been flown off the island before PNG police could investigate. The four men no longer work for the company.

7.30 has sought a comment from PNG authorities.

The Immigration Department told 7.30 in a statement that it could not comment on the contract arrangements between Wilson Security and its employees and that is does not have a "direct contractual relationship with Wilson Security in regards to regional processing operation on Nauru and PNG".