The US FAA has issued a new order to airlines to speed up inspections for all Boeing Next Generation 737s after finding new evidence that loose parts in the wing leading edge slat tracks is a wider problem than initially thought.

The emergency airworthiness directive (EAD) issued on 28 August requires airlines to perform a detailed or borescope inspection within 10 days, and a one-time torquing of the nut and bolt in the downstop assembly for the slat track within 24 days.

The order, which supersedes an EAD issued on 25 August, includes carriers all models of the 737NG, including the -600, -700,-700C, -800, -900 and -900ER.

The warning comes after a China Airlines 737-800 was destroyed by a fire caused by a fuel leak in Naha, Japan on August 20. An initial investigation showed that parts came loose in the assembly that serves as a downstop when the slat track deploys. As the slats were retracted, the loose parts pierced the fuel tank in the wing, according to the FAA.

Five days later, the FAA issued the first EAD to complete an initial inspection within a 24-day period. But feedback from the inspections quickly revealed a wider problem, with multiple aircraft reporting loose parts in the slat track assemblies. “Additionally, in one case, the slat can was damaged,” the FAA directive says.

Boeing, meanwhile, is continuing to collect data about the problem and decide whether an engineering fix will be necessary, a spokeswoman said.