A vomiting virus outbreak has affected thousands of children in Germany over the last few days, and according to the country’s health authorities, the number of children with vomiting and diarrhea has now increased from about 4,500 to as much as 8,400.

According to reports, the outbreak occurred when the children consumed food from school cafeterias or daycare centers. However, Berlin’s health department said that the illness  was moderate in the majority of cases and most of the affected children recovered in two days without requiring hospitalization, the  Associated Press reported.

On Saturday, officials in Berlin and the neighboring states reported a further outbreak of the mysterious virus. They said that new gastroenteritis cases had been reported and that the investigation to ascertain the exact cause of the outbreak was still under way.

Christian Post reported citing authorities that scientists were conducting a range of laboratory investigations in order to determine what exactly the cause of the severe outbreak among thousands of children could be.

German news agency DAPD said that at least 16 cases of norovirus had been confirmed in the state of Saxony. Noroviruses are transmitted through fecally (fecal–oral route) contaminated food or water, person-to-person contact, etc. These are the most common causes of viral gastroenteritis in humans.

Outbreaks of norovirus infection generally take place in closed or semi-closed communities, such as long-term care facilities, overnight camps, hospitals, prisons, dormitories and cruise ships, where the infection could spread quickly either by person-to-person transmission or through contaminated food.

According to WebMD, norovirus infection is also called food poisoning at times, with symptoms including nausea, vomiting (mostly in children), diarrhea and stomach cramps. Like most viruses, norovirus does not require antibiotics. For healthy individuals, the symptoms go away in a couple of days.

However, it is important to remain hydrated and avoid sugary drinks which could make diarrhea worse.

The government-affiliated Robert Koch Institute told the AP Friday that all the facilities where the outbreak occurred were believed to have received food from a single supplier. A theory has been built up suggesting that a single food item from one particular supplier could be the culprit.