Officials are investigating a possible link between seeds sold by a UK firm and an E. coli outbreak in France.
News agency AFP said 10 people have been affected by E. coli in Bordeaux.
It is thought a number of them had eaten rocket and mustard vegetable sprouts, believed to have been grown from seeds sold by Thompson and Morgan.
The Ipswich-based company told the BBC it had no evidence of a link. The Food Standards Agency (FSA) said no E. coli cases had been reported in the UK.
However, it has revised its guidance and is advising people not to eat raw sprouted seeds, including alfalfa, mung beans (or beansprouts) and fenugreek.
The agency said these should only be eaten if cooked until steaming hot throughout.
A spokeswoman for Thompson and Morgan said the company sold “hundreds of thousands of packets of these seeds” throughout France, the UK and other parts of Europe every year.
“We are very confident the problem is not with our seeds. People can still grow these seeds and use these seeds with absolute confidence,” she said.
“For such a small number of people to have been affected, it does suggest that the problem is perhaps in the local area, how the seeds have been handled or how they have been grown, rather than the actual seeds themselves.”
The company was co-operating fully with investigations, she added.
Paul Hansord, the company’s managing director, said: “We make sure that everything we do is to a high standard.”
He said the firm bought its seeds in bulk from suppliers around the world. The affected seeds may have been sourced from Italy.
Thompson and Morgan also said they did not raise any seeds, instead selling packets via mail order to gardeners.
Seven of those affected by the E. coli outbreak, who ate the sprouts at a country fair at Begres near Bordeaux, needed hospital treatment.
The FSA says it is asking the company for more information about the seeds.
There is no suggestion of a link to the German E. coli outbreak, which came from bean sprouts grown on an organic farm, but two people are said to be infected with a similar strain.
Frederic Lefebvre, France’s secretary of state for consumer affairs, was quoted by AFP recommending “consumers who bought these same products not use them”.
Mr Lefebvre added: “The link between the symptoms and eating of the sprouts so far has not been definitively established.”
The sale of the three seed types – mustard, rocket and fenugreek – has been halted in France.
Thompson and Morgan have provided samples of these seeds to investigators in the UK.
An FSA spokesman told the BBC: “We have been in contact with the French authorities about this outbreak and are aware that a UK business has been named in connection with it.
“No cases of food poisoning have been reported in the UK linked with the outbreak in France but we are in close contact with the Health Protection Agency.
“We have asked for further information from the French authorities with regard to the three named type of seeds to help us carry out investigations in the UK.”