WASHINGTON DC, US - The head of the National Highway Traffic Safety Administration says there is no estimated time frame for when it will complete its ongoing investigation into the Chrysler Group’s fix. The investigation of 1.56-million Jeeps is being carried out for fire risks that safety regulators say are caused by gas tanks that leak after rear-end collisions. NO CHANGEThe agency said it isn’t changing how it approaches recalls despite the disputes. NHTSA Administrator David Strickland said the agency continues to be in talks with Chrysler one month after Chrysler initially challenged the agency’s request to recall 2.7 million vehicles according to the Detroit News.He disputed Chrysler’s contention that its decision to install trailer hitches on some Jeeps won’t help protect gas tanks — which are located behind the rear axle — in some high-speed crashes.On June 18, Chrysler declined NHTSA’s formal request that it recall 2.7-million older Jeep SUVs for what the agency sees as fire risks. Chrysler maintains that its vehicles are safe, and says most of the crashes cited by NHTSA were high-speed crashes.Chrysler eventually agreed to recall 1.56 million Jeep models and install a trailer hitch assembly to protect the gas tank.