Food poisoning has struck Australia’s detention centre on Manus Island, with up to 100 asylum seekers and refugees in detention struck by diarrhoea and vomiting.

The outbreak appears confined to Delta compound.

“The medical centre was full of Delta guys,” one refugee told Guardian Australia. “They sent them in five groups there, they gave them medication and sent them back because there’s not enough space down in the clinic.”

Food has been an ongoing issue for the men in detention, with some complaining it is “inedible”.

They allege when visitors arrive at the centre – department officials, ministers, human rights groups – the food temporarily improves, before reverting.

Men in detention also regularly post photos of out-of-date food they say they’ve been served, or question its provenance.

One man posted a photo of his meal on 6 October: “Today’s lunch. If someone finds out what kind of animal’s meat it is please let me know.”

In August, the ABC revealed the Australian Department of Immigration and Border Protection ordered centre manager Transfield not to distribute $30,000 worth of muesli bars inside the detention centre because they were branded with the logo of the company that made them: Freedom Foods.

Guardian Australia has approached Transfield for comment.

Meanwhile, the supreme court of Papua New Guinea has reserved judgment in a case brought before it contesting the constitutionality of the Australian-run detention centre on Manus.

The case challenges the memorandum of understanding between Australia and PNG that re-established offshore processing in PNG in 2012, arguing the detention of asylum seekers violates section 42 of the PNG constitution which protects personal liberty as a “right of all persons”.

Lawyer representing the detained asylum seekers Ben Lomai said the men could not be detained because they had not broken any laws in PNG, nor had they entered the country illegally.

“The court noted ... that all the asylum seekers were forcibly transferred against their will from Christmas Island to Manus Island,” he said outside court. “The court further noted that the asylum seekers have never committed criminal offences to warrant their detention.”

Lawyers for the PNG immigration department said administrative arrangements between Australia and PNG over refugees were ongoing.

The court retired on Thursday to consider its decision.