Jun. 13, 1998 >> 6:39 am GMT Swiss Mystified by Surge of Radioactivity Reuters 12-JUN-98 By Elif Kaban GENEVA, June 12 (Reuters) - Swiss scientists said on Friday they and international colleagues were urgently trying to find out what caused a sudden sharp rise in levels of radioactivity in Switzerland and neighbouring France at the beginning of June. The unexplained surge on June 1 and 2 was not thought to pose a health risk, but it was the highest level in the 12 years since 1986's Chernobyl nuclear disaster, said Heinz Surbeck, deputy head of the Swiss radioactivity surveillance office. The contamination, borne on southern winds, might have been caused by fallout from the Chernobyl disaster reintroduced into the environment, or a possible accident, he said. As of Friday, Surbeck said radioactivity levels were back to normal from levels over 1,000 times above normal in early June. But he said recent French media reports about the radiation surge had caused a health scare in Switzerland. ``We've been getting many calls from the public -- pregnant women calling to say they're scared for their babies and people asking if it's okay to go to Ticino for holiday,'' said Surbeck, referring to the Italian-speaking southern Swiss canton. ``But we hope it's all over now,'' he told Reuters. The Swiss pride themselves on their clean environment and good air quality. The mountainous country has set up a vast network of radioactive monitoring since Chernobyl. Gennady Sushkevich, a medical doctor at the environmental health office of the World Health Organisation, said the levels were not dangerous and too low to contaminate the food chain. Surbeck said the contamination was caused by Caesium-137, which he said was the ``signature'' of Chernobyl and may suggest fallout from it. But he said the levels were 10,000 times below the concentration released by the Chernobyl nuclear plant in Ukraine on April 26, 1986, the world's worst nuclear disaster. The ensuing radioactive cloud poisoned vast areas in Russia, Ukraine and Belarus and drifted over parts of Western Europe. In May, France's independent CRII-RAD laboratory said it found high levels of Caesium-137 high in the Alpine mountains of Austria, France, Italy and Switzerland and called for regular monitoring of water and food for possible contamination. Scientists were mystified by the unexplained surge. ``The French are working very hard to find the source. Until they find the source, everybody will be nervous,'' said Manfred Hoefert, an expert at the European Particle Physics Laboratory CERN on the French-Swiss border. Possible sources could include a nuclear reactor, an accident or burning of a Caesium-137 source -- used for medical and industrial purposes -- that may release it into the air. Surbeck said samples taken showed radioactivity levels in southern France of 1,000 to 2,000 microbequerels per cubic metre detected by filters in place for one day. Those findings and Swiss surveillance pointed to similar high levels in Switzerland early in June, he added. The normal level is between two to three microbequerels per cubic metre. The southern side of the Alps were affected more than the north as the contaminated cloud hovered there after winds blew the radioactivity from south or southwest of Switzerland -- anywhere from southern France or Italy to north Africa. Copyright 1998 Reuters Limited.All rights reserved.