Eighty-nine Iraqi police needed medical treatment after an outbreak of sickness and diarrhoea at a base in central Iraq, health ministry officials say.
They say infected water is the most likely cause of illness in the town of Numaniya. The US military says some 200-300 people are affected.
Iraqi ambulances and US helicopters took the men to hospitals, and samples of food and water were being tested.
Iraqi and US officials denied earlier reports that some of the men had died.
The policemen started falling ill soon after breaking their daylight Ramadan fast on Sunday, officials said.
There had been suggestions that the suddenness and severity of the sickness pointed to deliberate poisoning.
The outbreak happened in the 4th police division - a largely Shia unit.
It is currently stationed in Numaniya - about 80km (60 miles) south-east of Baghdad.