Manufacturing activity in the New York area slipped in September, but remained positive in the aftermath of Hurricane Katrina, the New York Federal Reserve Bank said Thursday. The bank's Empire State Manufacturing index fell to 17.0 in September from 23.0 in August. Readings over zero indicate expansion. The decline was roughly in line with expectations. Economists were expecting the index to slip to 16.6. The biggest impact of Katrina came in the form of higher prices. The price index jumped more than 20 points to 53.4 in September, its highest level since March. Expectations of price increases over the next six months jumped to record highs.