Growth in India's infrastructure industries slowed down to 5.1 per cent in September from 5.8 per cent a year ago, but bounced back from a dismal 2.3 per cent in August this year. The growth in six core industries - crude oil, petroleum refinery products, coal, electricity, cement and finished carbon steel - contracted also for the April-September period to 3.9 per cent from 6.9 per cent in the first half of the previous year.