Bulgarian Health Minister Assen Medzhidiev said most of the survivors were in very bad condition.

“They have suffered from lack of oxygen, their clothes are wet, they are freezing, and obviously haven’t eaten for days,” Medzhidiev said.

The truck was found abandoned on a highway near the capital, Sofia on Friday. 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 migrants. Bulgarian media reported they all were from Afghanistan.

Bulgaria, a Balkan country of seven million and the poorest member of the European Union, is located on a major route for migrants from the Middle East and Afghanistan seeking to enter Europe from Turkey. Very few plan to stay, with most using Bulgaria as a transit corridor on their way westward.

Bulgaria has erected a barbed-wire fence along its 259-kilometer (161-mile) border with Turkey, but with the help of local human traffickers many migrants still manage to enter.

An earlier tragedy in Britain involving the deaths of migrants in the back of a truck saw members of an Irish-Romanian gang handed hefty prison sentences.

In October 2019, police found the bodies of 39 people inside a refrigerated 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.

Among those later convicted were Co Armagh man Ronan Hughes and Gheorghe Nica from Basildon, Essex. They were described as playing "leading roles" in the smuggling conspiracy and were jailed for 20 and 27 years respectively in January 2021.