Papua New Guinea's prime minister says his government still hasn't got a clear picture of an alleged rape incident at the Manus Regional Processing Centre.
But Peter O'Neill says they do know that alcohol played a part in what did transpire in the incident in mid-July.
Three security guards working for Transfield Services, which is contracted by Australia's government to run the centre, have been accused of raping a female worker at the centre.
Manus police continue to investigate.
The provincial police commander, Alex N'Drasal, said the investigation has been hampered first by the swift removal of the expatriate guards from the country, and then by the centre failing to cooperate with the police.
The prime minister has ordered that the alcohol ban at the Manus centre be effectively enforced and for regular alcohol and drug tests to be undertaken.
Mr O'Neill says the incident being probed is not the first time they have heard of inappropriate expatriate behavior as a result of alcohol consumption, and it has to stop.
He indicated that because the company in charge of contract personal have not maintained discipline, PNG's Chief Migration Officer will impose stricter controls.
Mr O'Neill says any staff who break the rules and are found to consume alcohol or drugs will be dismissed.
He adds that the foreign workers at Manus are very highly paid so he is sure they can go without alcohol while on contract.