Shanghai Composite index down 2.1% at midday break

HONG KONG (MarketWatch) -- Mainland Chinese shares extend losses in the Tuesday morning session, with sharp retreats in commodity producers further pressuring markets already weighed by fears of policy tightening, especially in the property sector. At the midday break, the Shanghai Composite Index had dropped 2.1% to 2,906.35, while the CSI 300 index, the underlying benchmark for index futures, shed 2.1% to 3,104.85. Shares of Baoshan Iron & Steel Co. /quotes/comstock/28c!e:600019 (CN:600019 6.83, +0.39, +6.06%) dropped 3.8% and Shandong Nanshan Aluminium Co. /quotes/comstock/28c!e:600219 (CN:600219 10.30, -0.10, -0.96%) slid 3.4%. Among property names, Beijing Vantone Real Estate Co. /quotes/comstock/28c!e:600246 (CN:600246 6.13, +0.02, +0.33%) shed 2.1%, reflecting fears that Chinese authorities may impose more restrictive measures on the sector, including a property tax. Meanwhile, Hong Kong shares continued to trade lower, with the Hang Seng Index down 1%.