MEDFORD, Okla. (AP) — Officials at an Oklahoma natural gas company say crews are making progress toward containing a lingering propane gas leak at a fuel-storage plant. ONEOK Incorporated spokeswoman Megan Washbourne said Saturday that efforts to cap the leak were ongoing, and officials didn't have a timeframe for when workers might be finished. Washbourne says monitors indicate the levels of gas in the air are zero, and officials expect the readings to remain low. The leak began Tuesday and prompted a voluntary evacuation of the 1,000 residents of Medford, about two hours northwest of Tulsa. City Manager Dea Kretchmar on Friday estimated that 10 to 15 percent of residents had left. The Environmental Protection Agency says there was concern the propane could start a fire and threaten a neighboring fertilizer facility.