"This is the food they give us, always like this, always disgusting," another asylum seeker said. "They treat us like animals, worse than animals."

Transfield Services, which operates the centre, did not return repeated calls and emails. But two Transfield staff on Manus Island separately confirmed that the teeth had been found and a complaint lodged.

"We know about that," one said. "People are talking about it."

It is not known from whose mouth the teeth came or how they came to be in the food.

They appeared to be stained red with betel nut juice: the nut is widely chewed on the island, mixed with powdered lime and mustard stick.

Several asylum seekers refused to eat lunch after the teeth were found.

It is not the first time teeth have been found in food in the detention centre. In 2013, Amnesty International reported that a tooth had been found in a meal served in the detention centre.

And the discovery of the teeth on Sunday came after a mass outbreak of food poisoning affecting up to 100 asylum seekers and refugees in the detention centre on Friday.

Transfield staff initially tried to tell asylum seekers they were struck by gastroenteritis and diarrhoea - all of them on the same day - because they did not wash their hands before eating. Staff have since conceded to asylum seekers they were food-poisoned.

One asylum seeker said detention centre staff had told him that since the outbreak, insects had been found in food, and food had been discovered stored in unhygienic conditions.

"They are going to have a big meeting to check samples of food everyday from the beginning, such as preparation, loading to distribution and serving," he said. "All of this is going to happen tomorrow or the next day."

Hygiene has been a consistent problem on Manus. Soap often runs out in dispensers in toilets, and replacements are slow to come to the island. Toilet paper is also often in short supply, asylum seekers have said.

In January, there was no running water in the detention centre for several days.