Residents of the Highlands at Rye, a 99-unit apartment building in Rye whose lower floors flooded in Tropical Storm Irene, are still prohibited from returning to their apartments. During the storm, a fuel-oil tank ruptured and leaked as much as 2,000 gallons of fuel. The Westchester County Health Department said Thursday that tests showed “elevated levels of oil-related compounds that were released into the air.” Tenants have been staying in area hotels since the storm, at the expense of the building’s owners, R.A. Cohen and Associates, Inc. The company is scrambling to make arrangements for 28 residents whose hotel reservations are set to expire Friday. The Health Department will continue to oversee air-quality testing to determine when the residents can return to the building.