Four children, including a baby girl, were among 71 migrants found dead in a truck on an Austrian highway and three people have been arrested in Hungary in connection with the tragedy, Austrian police said on Friday.
At a news conference in the town of Eisenstadt, Hans Peter Doskozil, police chief for the province of Burgenland, said one Syrian travel document had been found among the victims but that it was too early to say from which countries the entire group had come.
Of the 71 dead, 59 were men, 8 were women, and four were children, including a girl estimated at 1-2 years old and three boys of roughly 8-10 years.
"We currently have three people under arrest in Hungary... and expect that that this is the trace that will lead us to the perpetrators," Doskozil told reporters, making clear that the people being held were not ring leaders.
The refrigerated truck was found by an Austrian motorway patrol near the Hungarian border just before lunchtime on Thursday, with fluids from the decomposing bodies seeping from its back door.
The vehicle had come to Austria from Hungary and is believed to have been parked on the highway for at least 24 hours before it was discovered.
Doskozil said there were "signs" that a Bulgarian-Hungarian trafficker ring was behind the deaths. Of the three people arrested in Hungary, one was Bulgarian-Lebanese, another Bulgarian and the third of Hungarian nationality.
Thousands of people from countries like Afghanistan or Syria have fled through the Balkans to Austria, pushing the number of asylum requests to 28,300 in the first six months of this year - more than the total for all of 2014.
Austria's Interior Minister Johanna Mikl-Leitner said the best way to handle the refugee crisis was to create legal pathways into Europe, rather than stricter border controls.
The 28 member states of the European Union have not yet agreed on introducing binding quotas for the distribution of refugees. Leaders of the EU declared this week that it has "failed" in the face of human agony on its frontiers.
Meanwhile, the U.N. refugee agency UNHCR said on Friday the number of refugees and migrants crossing the Mediterranean to reach Europe has passed 300,000 this year, up from 219,000 in the whole of 2014.