A mass outbreak of suspected food poisoning has caused "carnage" across two university halls in New Zealand, with reports of early morning queues for toilets, vomit dripping down building windows and students abandoning exams to dash to the loo.

More than 100 students reported being struck down with vomiting and diarrhoea at two University of Canterbury student residences on Sunday night, the university confirmed on Tuesday.

The cause of the illness was yet to be determined, but students at University Hall and Ilam Apartments - both run by UniLodge - said they began feeling sick on Sunday evening, after eating the catered chicken souvlakia dinner, local news outlet Stuff reported.

Students have described to New Zealand media waking in the night with terrible stomach pain and rushing to the toilets, only to be met with queues of fellow students feeling similarly unwell. Some did not make it and vomited off their balconies, leaving a film of fluids splattered on the windows.

One student, who remained anonymous, told The Press she had used the toilet more than a dozen times on Monday morning, and later soiled herself at the university library because the toilets were full. Plum Olsen and her boyfriend, Lincoln Christensen, told the paper they had not slept after eating the chicken dinner because they had been so ill.

Meanwhile, students reported abandoning exams partway through because they needed to regularly use the bathroom, while others had been too unwell to attend at all.

"I kept going in and out of the room so I just decided to leave. It was carnage," one told Stuff.

Students who were unable to sit exams due to illness could apply for special consideration and may be offered a resit for exams in the coming weeks, the university said in a statement.

The national public health service would help investigate the cause of the illness, the university said, while those affected could request electrolytes, bottled water and packaged meals from UniLodge.

In a statement to the Guardian, UniLodge said it was aware of some students at its residences becoming ill and was offering them support.

It said it was working closely with the health service, university and the University of Canterbury Student Association - which it said provides catering to the halls - to investigate the situation.

In a separate statement, the students' association president, Luc Mackay, said the "investigation is still ongoing, and the cause has not been determined".

Mackay said the association was working closely with the university to minimise the impact on affected students.