Initial tests on bean sprouts from an organic farm in Germany are negative for the E. coli strain that has killed 22 people in Europe.
The agriculture ministry for Lower Saxony, in Germany's north, said on Monday that 23 of 40 samples from the farm suspected of harbouring the bacteria have tested negative. It said further tests are still ongoing.
Ilse Aigner, the German agriculture minister, said a warning remained in place for consumers over sprouts, tomatoes, lettuce and cucumbers.
Previously Gert Lindermann, the region's agriculture and consumer affairs minister, said a link had been found between the farm and the outbreak.
Hans Gert Hahne, a spokesperson for the state agriculture ministry in Lower Saxony, also said the farm had been "caught perhaps being a bit sloppy".
"He works honestly, it is a normal medium-sized company and he can't do anything about it but it was just bad luck that he is the source and as a result his whole method of work is being turned upside down," Hahne told the Reuters news agency.
But Klaus Verbeck, managing director of the Gaertnerhof Bienenbuettel farm, which lies 70km south of Hamburg, said he could not understand the accusations levelled at the centre.
"I can't understand how the processes we have here and the accusations could possibly fit together," he told the Neue Osnabruecker Zeitung paper on Monday.
"The salad sprouts are grown only from seeds and water, and they aren't fertilised at all. There aren't any animal fertilisers used in other areas on the farm either."
Health officials have continued to warn people in Germany against eating any sprouts and to be careful with fresh tomatoes, cucumbers and lettuces.
The European Commission has said it will ask member states to back special "compensation" for farmers whose sales of fresh produce have evaporated amid the outbreak.
EU agriculture ministers are due to hold an emergency meeting on Tuesday to discuss the crisis and its impact on vegetable producers.
The ministers "will be taking stock of the situation of the EHEC [strain of E. coli] outbreak both from the market perspective and also food safety," Marton Hajdu, spokesman for the Hungarian presidency of the European Union, told the AFP news agency.
The outbreak has caused chaos among Europe's vegetable growers after Germany warned against eating raw cucumbers, tomatoes or lettuce, particularly in the north of the country.
Initial accusations that the outbreak stemmed from Spanish cucumbers also caused diplomatic tensions.
Spanish farmers have complained that the accusations were having a devastating financial effect.