Outbreak of E. coli in Germany and France may have come from seeds from Egypt, the European Centre for Disease Control and Prevention said.
A report said there were still "considerable uncertainty", but fenugreek seeds imported in 2009 and 2010 "had participated in the two epidemics."
More than 4,000 people were infected during the outbreak of Germany, 48 died.
Investigators traced the source back to a farm in soybeans Bienenbuettel, Lower Saxony.
The epidemic has struck 15 people in Bordeaux and was linked to the seed sold by a company in the UK - Thompson and Morgan, although the company said it had no evidence of a link.
Both outbreaks involved the rare strain of E. coli called O104: H4.
The European Centre for Disease Prevention and Control (ECDC) said the strain was so rare in humans is unlikely that households have been isolated incidents and both were related to feeding the seeds to germinate.
Other studies have examined whether the source of infection was contaminated sites, or if they had been supplied with contaminated seeds.
The report said the outbreak was linked to the Bordeaux seeds exported by Egypt in 2009 to a company in Britain and then sold to France. The outbreak of the German came from seeds imported in 2010, he said.
The report added there could be more outbreaks of deadly E. coli, "Other potentially contaminated seeds are still available within the European Union, and perhaps beyond."
The ECDC and the European Food Safety Authority, "We advise consumers not to increase their consumption of sprouts and eat the sprouts or shoots, unless they are fully cooked," until investigations are complete.