A ferry crew found 25 migrants in a refrigerated container on a boat sailing from the Netherlands to Britain on Tuesday, emergency services said.
The cargo vessel bound for Felixstowe returned to the Dutch port of Vlaardingen, near Rotterdam, as soon as the stowaways were found, they said in a statement.
The people found in the container received medical attention at the port and two were taken to hospital for further treatment for possible hypothermia.
The discovery comes the month after 39 Vietnamese people were found dead in a refrigerated truck in Britain, again laying bare the risks of illegal migrant routes to