Bulgarian police have arrested seven people, an official said Saturday, a day after the bodies of 18 Afghans were found in an abandoned truck outside the capital Sofia.
Bulgaria’s deadliest recorded people smuggling incident comes as it struggles with an increase in illicit border crossings.
The truck was transporting 52 people hidden under wooden planks, and 18 died from suffocation, initial investigations showed.
Investigators discovered a gruesome scene with bodies scattered on the grass around the vehicle.
The group of Afghans was coming from Turkey and headed for western Europe.
Four Bulgarians have already been detained as suspects, and three fresh arrests were announced Saturday.
“I can confirm seven people have been arrested,” an interior ministry official told AFP.
Another government official said the suspected ringleader was among those arrested. He had earlier received a suspended jail sentence of five months for people smuggling.
The government has proposed tightening laws on people smuggling as the majority of smugglers are just fined or get suspended prison sentences.
The 34 people who were rescued on Friday were taken to hospital.
Some of them are being treated for carbon monoxide poisoning after having inhaled exhaust pipe gases as their hiding place was not well insulated, according to Spas Spaskov, a senior doctor at the Emergency Hospital Pirogov in Sofia.
“The oxygen they were getting was very limited, and they had no water, that’s why they are severely dehydrated. They did not eat for several days,” he told the Nova private TV channel.
EU-member Bulgaria, which serves as a gateway into the bloc, has been trying to tighten security to stop a rising number of people seeking to cross the border.
The poor Balkan nation has also faced mounting accusations it is abusing people trying to cross over from Turkey, with asylum seekers saying they have been pushed back, locked up, stripped and beaten.
Bulgaria has denied the allegations.