According to Bulgaria’s government, at least 18 people, including a child, were discovered dead in an abandoned truck.
The vehicle appeared to be illegally transporting approximately 40 migrants. The survivors were transported to a hospital for treatment.
According to the health minister, the people in the truck were cold, wet, and had not eaten in days.
It is believed to be Bulgaria’s deadliest migrant-related incident.
Bulgaria has long struggled to deal with large numbers of people attempting to enter the EU from Turkey.
The truck, discovered near the village of Lokorsko, 12 miles (20 kilometers) north-east of Bulgaria’s capital, Sofia, was illegally transporting migrants hidden beneath some wood, according to the interior ministry.
Asen Medzhidiev, Minister of Health, described the conditions inside the truck: “Those who were locked in this truck were suffering from a lack of oxygen. They were cold and wet, and they hadn’t eaten in days.”