Four people have been arrested by Hungarian police over the discovery of the bodies of 71 migrants, thought to be Syrian, in an abandoned truck in Austria.
Three of those arrested are Bulgarian and one is Afghan.
The bodies of 59 men, 8 women and four children were discovered on August 27 in an abandoned truck on an Austrian highway near the Hungarian border.
They are thought to have been dead for about two days.
Officials said the victims probably died after suffocating in the vehicle.
The truck was towed to a customs building with refrigeration facilities where forensic teams worked through the night to examine the bodies.
The local Austrian police chief said a travel document found on the vehicle suggested that the group were Syrian migrants.
“Our preliminary assumption is of course that they were refugees, possibly a group of Syrian refugees,” Hans Peter Doskozil, Burgenland province police chief, told reporters.
The truck had the branding of a Slovakian poultry company, Hyza, on it but the firm said it no longer owned the vehicle.
Hans Peter Doskozil said it was unusual for people smugglers to use a refrigerated vehicle.
“In our preliminary investigation we found that there was no ventilation possible through the sides of the truck,” he said, adding that the victims had probably suffocated.
Hungarian police said in a statement that they had “conducted house searches… and questioned almost 20 people as witnesses”.
Hans Peter Doskozil said one of the Bulgarians arrested is assumed to be the truck’s owner, while it is “highly likely” the other two are “the ones who drove the vehicle”.
He said there was “an indication we are talking about a Bulgarian-Hungarian human trafficking operation”.
“If you look at the organization of people traffickers, these are the lowest two levels of a criminal organization,” Hans Peter Doskozil added.
No details have been given about the Afghan detainee.
The truck, which has Hungarian number plates, is understood to have left Budapest on Wednesday morning, August 26.
It is believed to have been parked in the lay-by between Neusiedl and Parndorf for at least 24 hours before police discovered the bodies.
Tens of thousands of migrants from conflict-hit states in the Middle East and Africa have been trying to make their way to Europe in recent months.
A record number of 107,500 migrants crossed the EU’s borders last month.
Some of them pay large sums of money to people smugglers to get them through borders illegally.