Health minister says 34 survivors, including five children, were rushed to hospitals and some were in critical condition.
Around 40 migrants were in the truck, with survivors rushed to hospital.
At least 18 people have been found dead in Bulgaria in an abandoned truck near the capital Sofia, officials said.
The truck was transporting timber and carrying refugees and migrants hidden in a compartment, the country’s interior ministry said in a statement on Friday.
Health minister Asen Medzhidiev said 34 survivors, including five children, were rushed to hospitals in Sofia and some were in critical, but stable condition.
“There has been a lack of oxygen to those who were locked in this truck. They were freezing, wet, they have not eaten for several days,” Medzhidiev told reporters.
The truck was found abandoned along a highway near the capital, Sofia.
The driver was not there, but police discovered the passengers in a secret compartment below a load of timber.
Authorities did not immediately give the nationalities of the people found.
Police were seeking to identify the truck’s drivers, who had fled, according to the interior ministry.
Bulgaria is situated on a route used by refugees and migrants from the Middle East and Afghanistan to enter the European Union.
Most do not stay in the country, but look to move on to richer countries in Western Europe, often via networks of smugglers.
In 2015, three Bulgarian truck drivers were arrested and later charged with the deaths of 71 migrants found dead beside an Austrian motorway.
In October 2019, British police found the bodies of 39 people inside a refrigeration container that had been hauled to England. Police said all the victims, who ranged in age from 15 to 44, came from impoverished villages in Vietnam and were believed to have paid smugglers to take them on a risky journey to better lives abroad.
Police said they died of a combination of a lack of oxygen and overheating in an enclosed space. The truck discovered in the town of Grays, east of London, had arrived in England on a ferry from Zeebrugge in Belgium.
