LONDON, Aug 16 - Thirty-one people, including several children, were discovered in poor health, packed inside a shipping container being unloaded at a dock in eastern England on Saturday morning, police said. One man has died and the others were being treated by ambulance crews at the scene and in hospitals, they added in a statement. The container was being unloaded at Tilbury docks in Essex from a ship that had arrived from Zeebrugge, Belgium. Tilbury, on the River Thames, is primarily a bulk cargo and container port and not such a prime target for illegal immigrants as those on the south coast, such as Dover. Essex police said they had started an investigation and were working with immigration and health authorities. No further details were immediately available.