One company head said: “A refrigerated unit like that one is built to be airtight to preserve what it carries.
“It can sometimes be used to transport flowers or plants, but normally fresh produce. If it’s chilled, the trailer temperature will be set to -5C, but if it’s frozen you’re talking about -25C.
“There’s little or no chance of survival if you’re in those conditions for any length of time.”
Officers bowed their heads as the lorry was driven away to a “secure location” at Tilbury Docks.
The lorry was registered in Bulgaria in 2017 by an Irish company, but it has not returned to Bulgaria since then.
British news reports say police were warned about the Essex port three years ago that “people smugglers were targeting Purfleet – the Essex port where the lorry container docked and that it was being used because it was “less busy” than other ports.
One migrant died five years ago and 35 others – including children – were rescued from a container at nearby Tilbury Docks five years ago.
One report said: “Workers heard screaming and banging from the 40ft container soon after a P&O ferry docked in the Essex port.”
Police are now working to identify the victims which they anticipate will be a “lengthy process”.
The Chief Superintendent is quoted as saying: “This is a tragic incident where a large number of people have lost their lives. Our enquiries are ongoing to establish what has happened.”
Britain’s Prime Minister, Boris Johnson said during PMQs that the perpetrators “should be hunted down and brought to justice”.
This case is now “the biggest disaster of its kind since 2000, when 58 Chinese stowaways died in a lorry travelling by ferry from Belgium to Britain”.
They were immigrants, who “likely died of asphyxiation after being trapped in the container for more than 18 hours”.
The driver in that case, Perry Wacker, was sentenced to 14 years in prison for his role in a people smuggling operation run by a Chinese gang.
In 2004, 23 Chinese cockle pickers in search of a “better life” drowned in Morecambe Bay, Lancs, when they were trapped by sweeping tides.