French health officials said tests on two of the eight showed an infection of the same strain of E coli which recently killed 44 people - all but one in Germany - and affected another 3,700 including Britons who had visited Germany.
Commerce minister Frederic Lefevre said the order involved fenugreek, mustard and arugula seeds linked to Ipswich-based Thompson & Morgan.
An investigation by France's competition, consumption and fraud prevention agency found two of the eight people taken to hospital had consumed sprouts from the three seeds at a school fair in the south-west town of Begles.
Thompson & Morgan said it sold "thousands of packets and had no reported problems".
"It is highly unlikely to be the seeds themselves but the way that they were used and handled," it said in a statement.
Managing director Paul Hansord said it bought seeds in bulk from around the world. He said the seeds under investigation may have come from Italy.
The Food Standards Agency said: "No cases of food poisoning have been reported in the UK linked with the outbreak in France but we have asked for further information from the French with regard to the three named type of seeds to help us carry out investigations in the UK."
It is possible to find E coli in seeds but the investigation must now check how the seeds were grown, who planted them and how the sprouts were prepared for consumption.