Factory activity in the U.S. Mid-Atlantic region rose in September to the highest level sinceJune 2007, a survey showed on Thursday. The Philadelphia Federal Reserve Bank said its business activity index was at 14.1 in September versus 4.2 in August. Economists polled by Reuters had forecast a reading of 8.0. Any reading above zero indicates expansion in the region's manufacturing sector. The survey covers factories in a region encompassing eastern Pennsylvania, southern New Jersey and Delaware.