The supermarket sector was firmly in the red on Monday after Tesco was forced to admit that it had over-stated its first half profit guidance by £250m.The company has suspended four of its executives, including the UK managing director, and said it plans to investigate the matter.The food retailer said the misstatement was due to booking revenue early and delaying costs and revealed there were preliminary investigations into its UK food business.Analysts responded to the news with shock, with Clive Black, Head of Research at Shore Capital, going as far as to say that the mistake must raise "fundamental questions" regarding the chairman's position.Sector peer Sainsbury was also heading south after Exane BNP Paribas cut its target price on the stock from 295p to 280p.The mining sector was also a heavy faller after China's finance minister squashed speculation that the government would boost stimulus.China's Finance Minister Lou Jiwei said the government will not make any major policy changes in response to weak economic data and downward pressure on growth in the world's second biggest economy.Glencore, Rio Tinto, Anglo American, Antofagasta and BHP Billiton were all in the bottom ten on the FTSE on Monday afternoon.Top performing sectors so far todayConstruction & Materials 4,005.73 +0.60%General Industrials 4,184.88 +0.33%Electricity 9,707.58 +0.22%Health Care Equipment & Services 5,972.66 +0.12%Food Producers & Processors 7,593.14 +0.09%Bottom performing sectors so far todayIndustrial Metals & Mining 1,466.22 -8.91%Food & Drug Retailers 2,912.04 -6.65%Mining 16,198.87 -2.77%Fixed Line Telecommunications 4,474.51 -1.42%Mobile Telecommunications 4,570.31 -1.03%