By Kate Kelland

LONDON (Reuters) - A single shipment of fenugreek seeds from Egypt is the most likely source of a highly toxic E. coli epidemic in Germany which has killed 49 people and of a smaller outbreak in France, European investigators said on Tuesday.

The European Food Safety Authority (EFSA) said additional European Union member states and other countries had or may have received batches of suspect seeds and urged the European Commission to make "all efforts" to prevent any further consumer exposure.

Consumers should not eat sprouts or sprouted seeds unless they are thoroughly cooked, it said.

More than 4,100 people in Europe and North America have been infected in two outbreaks of E. coli infection - one centered in northern Germany and one focused around the French city of Bordeaux.

Almost all of those affected in the first outbreak - the deadliest on record - lived in Germany or had recently traveled there. The infection has killed 48 people in Germany and one person in Sweden.

"The analysis of information from the French and German outbreaks leads to the conclusion that an imported lot of fenugreek seeds which was used to grow sprouts imported from Egypt by a German importer is the most common likely link," the EFSA said in a statement.

It said the contamination of the seeds with a highly toxic strain of E. coli had taken place "at some point prior to leaving the importer."

"Other lots of fenugreek imported from Egypt during the period 2009 to 2011 may be implicated," EFSA said, adding that investigations should be carried out in all countries that may have received seeds from the lots concerned.

EU government officials were meeting in Brussels on Tuesday to decide on their response to the investigations.

FECAL MATERIAL

"Given the possible severe health impact of exposure ...it seems appropriate to consider all lots of fenugreek from the identified exporter as suspect," the EFSA said in a report on its investigations.

The strain of E. coli infections identified in the outbreaks - known as STEC O104:H4 - can cause serious diarrhea and in severe cases kidney failure or death.

"The contamination of seeds with the STEC O104:H4 strain reflects a production or distribution process which allowed contamination with fecal material of human and/or animal origin," EFSA said. "Where exactly this took place is still an open question."

E. coli bacteria thrive in nutrient-rich environments like the guts of humans or cows. The STEC O104:H4 strain has been found to be particularly sticky, making it likely able to cling on to leaves, seeds and other foodstuffs.

The EFSA said the number of EU countries that had received parts of the suspected lots is much larger than previously known and added: "It cannot be excluded that other member states and third countries were supplied."

In western Germany, health officials are carrying out wide-scale E. coli tests in the municipality of Paderborn after renewed cases of the rare strain were reported among primary school pupils and canteen workers, shutting one school for a week.

More than 800 pupils, teachers, supervisors and pensioners are being tested for E. coli.