Six stowaways were caught on a Finnish ro-ro in the UK after calling emergency services in desperation.
The Sun reported that the African men had boarded owner Bore's 25,600-gt Bore Song (built 2011) in Zeebrugge, Belgium, last month.
When it reached Teesport in England, they dialled 999 and said: "We are stuck in a container."
The migrants had become desperate by 2 April after being locked in the container for more than a day following its arrival in the UK at the end of March.
They were suffering from dehydration.
The men were taken to hospital before being released into the custody of border immigration forces.
