 At least 18 people were found dead in Bulgaria in an abandoned truck near the capital Sofia, the Bulgarian Interior Ministry said on Friday. The truck was transporting timber and carrying an estimated 40 illegal migrants hidden in the load. It was found near the village of Lokorsko, some 17 kilometers northeast of Sofia. Health Minister Asin Medidziv told reporters that some of the migrants were in critical but stable condition. He said there had been a lack of oxygen to those who were locked in and that patients were freezing, wet and had not eaten for several days. The Health Emergency Center told state news agency BTA earlier that eight people were rushed to hospital in grave condition. Police were seeking to identify the truck drivers who had fled. Bulgaria is situated on a route used by migrants from the Middle East and Afghanistan to enter the European Union. Police do not stay in the country, the EU's poorest member state, but look to move on to richer countries in Western Europe, often using elaborate 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 December, Bulgaria was blocked from entering the EU's passport-free Schengen zone by Austria and the Netherlands over security and rule of law concerns, but the country will seek to gain entry again this year.