Initial tests conducted on sprouts from a north German farm probed as a possible source for a killer bacterial outbreak have proved negative, officials from the state of Lower Saxony said Monday. Tests conducted on 23 of 40 samples indicated they were free of the E. coli bacteria responsible for 22 deaths, the state\'s agriculture ministry said. \"Investigations are continuing,\" the ministry said, adding that it did not expect \"any short term conclusions\" into the probe, Gert Lindermann, Lower Saxony\'s agriculture and consumer affairs minister, announced Sunday that a link had been found between the farm and \"all the main outbreaks\" of the dangerous E. coli strain in the country. Klaus Verbeck, who runs the farm in Bienenbuettel, some 80 kilometres (50 miles) south of Hamburg, told the Neue Osnabruecker Zeitung he uses no fertilisers for growing a variety of sprouts and had no idea how they might have been contaminated. His farm has been ordered closed and all its products recalled, authorities said.