Investigators searching for the origin of a killer bacteria were attempting to track supplies made to a north German restaurant where 17 guests fell ill, the press reported here Sunday. The owner of the \'Kartoffelkeller\' restaurant in the Baltic seaport of Luebeck, Joachim Berger, told ZDF public television that health inspectors had carried out tests at the premises after three separate groups of people had fallen ill after eating there. More than 2,000 people have been taken ill over the past month, mostly in northern Germany, and at least 19 have died after being contaminated by the virulent enterohaemorrhagic E. coli (EHEC) with symptoms including stomach cramps, diarrhoea, fever and vomiting. Health officials, cited by Berger, said a family, a group of Danish tourists, and some women tax-inspectors were among the 17 who ate at his restaurant on May 13 and who contracted EHEC. Guests who became ill appeared to have eaten steak and salad. Bild am Sonntag newspaper said a 48-year-old woman tax-inspector later died, while eight remain ill, two of them critically. \"I have nothing to hide, I\'m sure everything is in order\" with the restaurant, the 67-year-old Berger told the newspaper. Inspectors had thoroughly examined his kitchens and taken stool samples from all his employees, Berger said. None of the staff, who ate the same food as the guests, had been ill, he added. Christian Seyfert, a spokesman for the consumer protection ministry in the region, told AFP that speculation about the restaurant\'s link to the outbreak was unfounded. Berger said his food supplies came from a wholesaler in Moelln who obtained them from the central food market in Hamburg, the northern port where numerous cases of EHEC have also been reported. German Health Minister Daniel Bahr, who on Sunday was to visit Hamburg\'s Eppendorf University clinic where many of the region\'s EHEC patients are being treated, has warned that the source of infection could still be active. \"Food health officials are working around the clock to identify the source of the infection,\" Bahr told the Ruhr Nachrichten newspaper on Saturday. \"But from earlier outbreaks we know that we can\'t always identify the source. \"It can\'t be ruled out that the source of infection is still active,\" he added, pointing to the need for continued vigilance as authorities still counsel against eating raw tomatoes, lettuce and cucumbers. Speaking to Bild am Sonntag, Bahr also the situation in a number of north German hospitals, especially Hamburg and Bremen, was \"difficult\" because of the high number of admissions, adding that other hospitals would be called upon to help. Hamburg\'s top health official, Senator Cornelia Pruefer-Storcks, told NDR radio-television that the number of EHEC cases appeared to be growing more slowly. Hamburg had registered 19 confirmed or suspected EHEC cases between Friday and Saturday, with one new case of full-blown haemolytic uraemic syndrome (HUS), a kidney-threatening condition, she said. At least 552 people have contracted HUS, according to the World Health Organisation (WHO). Earlier figures of infection for Hamburg had been much higher. Cases of E. coli poisoning have also been reported in more than 12 other countries, including Austria, Britain, the Czech Republic, Denmark, France, The Netherlands, Norway, Spain, Sweden, Switzerland and the United States. Each was related to German travel. A large majority of the patients are female, suggesting the source is \"probably something that women prefer more than men,\" Andrea Ellis, an epidemiologist at the WHO department of food safety, said in Geneva.