After some discussion he was persuaded to disembark so that the "Helmuth" could continue operations. Leaving demolition parties aboard the cargo vessels, Ritchie then took the Helmuth further downriver to check for other shipping, but the small ship grounded on a sandbar. Assuming the route was blocked, he returned to the two cargo ships on one of the expedition's small launches. It was at this stage, whilst conducting a final inspection, that he made the discovery of a large number of empty ammunition cases and discarded bullets in the holds of the cargo ships. Deducing that the German crew had armed themselves before they left their vessels, he suspected preparations were underway to ambush his force when it attempted to leave the harbour.