The growth of eight infrastructure industries slowed down to 3.1 per cent in July, against 4.5 percent in the same month last year, The slow down is attributed mainly to contraction in crude oil and natural gas production.The growth in July, however, was higher than the previous month when the core sectors had expanded by just 0.1 per cent. These eight infrastructure industries have a weight of about 38 per cent in the overall industrial production.Crude oil production contracted 2.3 percent and natural gas production fell 16.1 percent in July, according to the official data released today. But Petroleum refinery production expanded 5.1 percent in the month against 26 per cent in July 2012. Steel production grew 7 percent, while cement output was up by 0.8 per cent in July this year. Coal production slowed down 1.2 percent in July 2013, from 2 percent last year but electricity generation rose to 5.2 percent against 2.7 per cent in July 2012.Fertiliser output grew by 0.4 per cent in July. During April to July period, the growth of eight infrastructure industries slowed to 1.9 percent from 6.3 per cent in the same period last year.