Basildon Hospital said on its Twitter feed that it is “responding to a major incident”, adding: “A&E is open, but please be aware that waiting times may be extended.”
A spokeswoman for the hospital said they are providing treatment for 19 people including seven children. She added: “They are all currently being assessed.”
Essex Police were called after the people were found on the container, which arrived on a ship from Zeebrugge in Belgium and was being unloaded at 7.35am by Port of Tilbury authorities.
A police spokesman said: “Thirty one people, including adults and children of both genders, were found inside. One man has sadly died and the others have significant health problems. They are being treated by ambulance crews and are being taken to local hospitals.”
Police are dealing with the incident alongside staff from Port of Tilbury, UK Border Force and the East of England Ambulance Service, the spokesman said, while a casualty bureau is being set up.