The company providing medical services to detainees in the Australian-run immigration detention on Manus Island has reportedly been operating illegally under a government contract for the past three years.

International Health and Medical Services (IHMS), which is owned by multinational company International SOS (ISOS), runs a medical clinic on the island for the Australian government.

Sources have told SBS News a meeting was held on Thursday informing detention centre staff the Manus Island health services were likely to be closed because they had not been registered by the Papua New Guinea Medical Board.

As a result the 103 staff working at the centre, including 54 Papua New Guineans and 37 Australians, had allegedly been employed illegally.

According to Papua New Guinea Today, IHMS, was only granted temporary licenses to provide a day clinic out of makeshift containers in 2013.

An Independent Review Committee has handed down preliminary findings stating ISOS "intentionally breached" PNG law in their operation of the Manus Island health services.

"Knowingly, ISOS has operated the Manus facility thus seriously breaching the PNG Medical Registration Act 1980," Papua New Guinea Today reported.

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However, IHMS disputes these claims saying the company was registered to operate in Papua New Guinea, including Manus Island.

In a statement provided to SBS News, IHMS said it was told in May 2016 the PNG Medical Board "had concerns regarding the licensing of the medical clinic on Manus Island".

"Since being made aware of the issue, IHMS has submitted all required documentation to the PNG Medical Board to enable to licensing of the Manus clinic, and has sought guidance from the PNG Medical Board on who should hold the license," the statement said.

"Together with the Department of Immigration and Border Protection, IHMS has sought to arrange for the PNG Medical Board to travel to Manus Island to finalise registration.

"This offer has not been accepted to date."

IHMS described the accusations it was not properly registered in PNG as “unfounded” and said it had encountered other struggles while operating in the country.

"IHMS was informed by the PNG Chief Secretary that a report on its investigation would be issued to us within a week and we could then work collaboratively with the PNG government to resolve any outstanding issues.

"This report has never been issued and our multiple requests to meet with the PNG Chief Secretary, the PNG Minister for Health, and other government officials have been ignored."

IHMS also said its staff were registered "in accordance with PNG laws and regulations".

In contrast to IHMS's statement, the PNG government-appointed committee said ISOS country general manager Mark Delmonte had admitted the company was not registered and as a result had been deported and a full investigation was launched.

PNG Health Minister Michael Malabag had also reportedly made multiple requests for the company to formally apply for registration to run medical services on the island.

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He also reportedly recommended ISOS not be given registration and on January 16 wrote a letter to PNG Prime Minister Peter O'Neill saying: "I strongly suggest that we allow ISOS to withdraw their services on the basis of them breaching the Medical Registration Act as it is a serious criminal offence".

A spokesman from Australian Border Force did not answer SBS News's questions about the future of the medical clinic, saying only that "the registration of medical facilities in Papua New Guinea is the responsibility of the Papua New Guinean Medical Board".

SBS News has sought comment from International SOS.

There has been strong criticism of the medical services offered to detainees on Manus Island, as well as the bureaucratic processes in place.

An inquest into the death of Iranian asylum seeker Hamid Khazeai in 2014 heard it took almost 24 hours for approval to be given for him to be transferred to Port Moresby, by which time he was took sick for a commercial flight.

It then took another 12 hours before an air ambulance took him to Port Moresby and from there he was immediately flown to Brisbane.

A witness, a former employee of International SOS, Dr Stwert Condon, told the inquest their requests for Mr Khazaei were ignored or over-ruled.

"The policy was to provide medical care as much as possible to people in these situations and provide first-world care, but there was a pressure regarding finances and budgets of doing air ambulance evacuations… and for people to travel to Australia,” Dr Condon told the inquest.

It is not the first time the Manus Island dentention centre has run afoul of PNG's laws.

In April 2016, the PNG Supreme Court ruled the Australian-run centre's operation was illegal and breached the country's constitution and said it must be shut down, but the centre continues to operate.