NASA engineers, preparing to fix a leak in a steering rocket system aboard the shuttle Discovery, worked Tuesday to track down the source of yet another possible leak in a different part of the ship.

The first leak was detected July 15 and traced to a half-inch "dynatube" fitting inside the shuttle's left-side orbital maneuvering system rocket pod, one of two mounted on either side of the ship's tail fin.The approved repair technique calls for cutting two holes in Discovery's aft payload bay bulkhead, then two more in the rocket pod's forward bulkhead so engineers can reach the leak.

Meanwhile, other engineers are looking into a possible leak around the 17-inch pipe that carries liquid hydrogen rocket fuel from the shuttle's external tank into the engine compartment.