Germany's consumer minister expressed deep concern Wednesday at an outbreak of poisoning by dangerous bacteria believed to have killed three women and left hundreds ill.

"This is really worrying," Ilse Aigner said on ARD public television. "We do not know what is the source (of the poisoning) and we cannot rule out there will be more cases."

According to the Robert Koch Institute (RKI), Germany's national disease agency, more than 80 people have become seriously ill in the past two weeks after ingesting enterohaemorrhagic E. coli (EHEC).

Across Germany, mostly in the north, there are hundreds of other suspected cases, including some 200 in the state of Schleswig-Holstein, 100 in Lower Saxony, and in Hamburg close to 50.

Three women, including two in their eighties, are believed to have died as a result over the past week, although tests have yet to confirm this.

RKI head Burger on Tuesday called the recent number of recorded cases "scarily high".

Normally in a year there are around 1,000 EHEC infections and some 60 cases of haemolytic uraemic syndrome (HUS), a life-threatening disease caused by EHEC infection.

According to the , HUS is characterised by and blood problems, with a of between three and five percent. It can also cause seizures, strokes and coma.

E. coli is commonly found in the gut of humans and warm-blooded animals. Most strains of E. coli are harmless but some, like EHEC, can cause severe , resulting in several outbreaks in recent years.

It is transmitted to humans primarily through contaminated foods such as raw or undercooked meat and unpasteurised milk, as well as by animal faeces getting into water and food and by cross-contamination during food preparation.