Casual apparel chain American Eagle Outfitters Inc on Wednesday announced a sharp 8.1 per cent fall in September same-store sales and warned a cotninued weak retail environment could impact earnings. The Pennsylvania-based company said consolidated same-store sales, which include American Eagle and Bluenotes/Thriftys stores in Canada, fell 10.1 per cent last month, with Bluenotes/Thriftys same-store sales plunging 30.2 per cent.