In Germany, health authorities groped in the dark in search of the source of the E coli infection with suspicions about bean sprouts being a potential carrier yet to be substantiated, as the death toll in Germany’s worst outbreak since the World War II rose to 25.

An organic farm in the state of Lower Saxony came under the suspicion of health authorities as a probable source of the outbreak after they discovered that it had directly or indirectly supplied bean sprouts to a number of restaurants and canteens in several cities in northern Germany where many cases of Escherichia coli infection were reported.

A restaurant in the Baltic Sea port city of Luebeck suspected of being a source of the infection also had received supplies of bean sprouts from the farm.

However, laboratory tests of bean sprouts from the farm in Uelzen showed no traces of the killer bacteria, Lower Saxony health ministry officials confirmed. More than half of 40 samples taken from the farm tested since Tuesday were negative, a spokesman for the ministry said in Hannover.

Nevertheless, investigators are continuing their examination of bean sprouts as a potential source of infection because the conditions in which they are grown are ideal for the breeding of the bacteria, the officials said. They also pointed out that a much larger E coli epidemic in Japan in 1969 was caused mainly by bean sprouts tainted with the bacteria.