Diarrhoea, vomiting and abdominal cramps in children could be a sign of coronavirus infection, UK researchers say.
The Queen's University Belfast team have been studying children and say this may be worth adding to the checklist of symptoms.
Currently, the officially recognised symptoms in the UK are a fever, cough and loss of smell or taste.
Anyone with any of these should isolate and get tested for the virus.
The US Centers for Disease Control already lists nausea or vomiting and diarrhoea among possible Covid-19 symptoms.
In the trial, nearly 1,000 children had their blood tested to see if they had recently caught coronavirus.
The results, published but not yet peer-reviewed at medRxiv, revealed 68 of the 992 children had antibodies to the virus, suggesting they had been infected with Sars-Cov-2 at some point.
Half of those who tested positive reported having symptoms.
Fever was the most common - reported by 21 of the 68 children who tested positive for coronavirus antibodies.
Cough was also common but less specific, being reported as commonly by children who tested negative as those who tested positive.
Gastrointestinal symptoms - such as diarrhoea, vomiting and abdominal cramps - were reported by 13 of the 68 children who tested positive for antibodies, and appeared to be significantly associated with coronavirus infection.
Loss of smell or taste was less common - reported by six of the children with antibodies.
None of the children in the study was seriously ill or needed to be admitted to hospital.
Lead researcher Dr Tom Waterfield said: "We know that, thankfully, most children who get the virus will not be very ill with it - but we still do not know how much children may be spreading it."
In the study, testing only those children with fever, cough or changes in smell or taste would have identified 26 out of 34 or 76% of the symptomatic cases.
Adding gastrointestinal symptoms would have identified nearly all - 33 out of 34 or 97% - of the symptomatic cases, he explained.
"We are finding that diarrhoea and vomiting is a symptom reported by some children and I think adding it to the list of known symptoms is worth considering," Dr Waterfield said.
A Department of Health and Social Care official said: "An expert scientific group keeps the symptoms of Covid-19 under review as we increase our understanding of the virus.
"Anyone in England experiencing the main symptoms of coronavirus - a high temperature, a new continuous cough, or a loss or change to sense of smell or taste - should get a test as soon as possible."