A Norwalk Islamic group announced today that it may sue the City of Norwalk for rejecting its plan to build a mosque in a residential area. City zoning commissioners last night nixed the proposal, which calls for construction of the Al-Madany Islamic Center at 127 Fillow St. Muslim community leaders say they were surprised by the panel's decision since they agreed to keep a popular farm house on the property. The original plan called for a 27,000-square-foot worship center, but city officials say the size was not appropriate for the neighborhood. Islamic center spokesman Farhan Memon says discrimination may have been a deciding factor. He also says local leaders paid $500,000 for the property and that they will continue to fight for their mosque. Norwalk Zoning Commission denies mosque permission