The relocation site of the world-famous Tsukiji Fish Market has been contaminated with far more toxic chemical materials than previously thought and around 2 meters of surface soil will probably have to be replaced, an advisory panel to the Tokyo Metropolitan Government said Monday. The metropolitan government is planning to relocate the market by 2013 to the Toyosu area of Koto Ward because the Tsukiji site has become too crowded and facilities there have aged. Gov. Shintaro Ishihara indicated the relocation plan could be delayed due to the contamination problem. A group of experts gathered at the metropolitan government's offices for a periodic conference to discuss the reduction of risk at the Toyosu site. Work to reduce the risk from chemicals include digging up the soil of the entire site to a depth of 2 meters and replacing it with new soil, as well as purifying subsoil water, according to the panel. In studies conducted from February to April, the metropolitan government detected benzene, which can be a cancer-causing agent, at up to 43,000 times the legally acceptable level. It also found that the groundwater of part of the site contained benzene at 10,000 times and cyanogen at 130 times the acceptable level. "(The detoxification work) would be one of the biggest projects ever undertaken in the nation," said Tatemasa Hirata, a professor of systems engineering at Wakayama University and chairman of the panel that consists of four experts. "There have been several cases of this level of groundwater contamination, though not very often," said Takeshi Komai, deputy director of the Institute for Geo-resources and Environment and another member of the panel. However, the experts agreed that detoxification is possible and intend to discuss prevention measures further in future meetings. Safety became an issue when Tokyo Gas Co., which formerly had a factory at the site, first disclosed that the land contains high levels of toxic substances, including benzene and cyanogen, in 2001. Since then, the metropolitan government has carried out investigations on the site and some detoxification work as well. The investigation is continuing, and further results are expected to be reported in June.