VIENNA, Aug. 30  (NsNewsWire) — The 71 dead migrants who were found Thursday in an abandoned lorry on a motorway in eastern Austria near Vienna died from lack of air, police said on Saturday.

It is hard to imagine how crowded the lorry was, as 71 people could not even stand together inside the middle-sized lorry, indicating each body only has a tiny space to breath in the darkness, reports Xinhua.

They all died from lack of air, but it was still unclear where they were originally from, and when they died, with details expected to be released in the next days, police told Xinhua.

The deadly journey of the lorry carrying 71 migrants, included 59 men, eight women, 3 boys aged 8-10, and one 1-2 year-old baby girl started from the southern border of Hungary with Serbia, before going through Hungary to Austria, according to Hungarian officials.

The truck was captured on camera in the south of Budapest at around 3 a.m. local time (0100 GMT) on Wednesday and was later spotted on camera near the Hungarian side of the border with Austria at around 9 a.m. (0700 GMT) on Wednesday.

The truck carrying Hungarian license plates was found by police parked around 50 km away from Vienna at the side of motorway in Austrian eastern state Burgenland on Thursday at around 6 a.m. local time (0400 GMT), and it was finally opened at around 11:30 a.m. (0930 GMT) when police found dead bodies inside the truck.

Inside the lorry, police found a document which could be traced to Syria, indicating the dead people might be from Syria.

Three Bulgarians and one Afghan have been arrested for their roles in the deaths of the 71 refugees, Gabor Schmidt, a prosecutor in Kecskemet, Hungary, said in a statement Saturday.

Schmidt said that based on information obtained to date, the people smugglers had picked up the refugees, who illegally crossed the Serbian-Hungarian border into Hungary, in Kecskemet, a city south of Budapest, and had transported them to Austria. The four men were apprehended on Thursday.

Discovery of the tragedy came the same day when the Balkan summit was held in Vienna to focus on migrant issue.

Speaking to the summit on Thursday, German Chancellor Angela Merkel said she was shaken by the death of the migrants found in Austria, urging “solidarity in the European spirit” to resolve the migration issue.

Austrian Chancellor Werner Faymann said that the tragedy was a perfect example of the need for quick solutions to deal with the torrent of migrants pouring into Europe.

“I am horrified and heartbroken at the latest loss of lives of refugees and migrants in the Mediterranean and Europe, ” United Nations Secretary-General Ban Ki-moon said, referring to the truck deaths.

Thursday’s truck tragedy in Austria came as the European Union (EU) member states are divided over an EU-proposed quota system designed to share the burden of accommodating refugees among EU member states.

Waves of refugees have been pouring from war-torn regions in north Africa, Middle East and central Asia into Europe in an almost daily manner. Frequent missions of patroling the sea and rescuing refugees from boats and placing them left south Europe’s coastal nations the first ones to be overburdened. Still, for many migrants, the coastal nations are only their first stop before heading north to west and central Europe.

European analysts said the root cause of migrant waves — conflicts, instability and poverty in north Africa, Middle East and central Asia — should be dealt with, which is among the long-term solutions to Europe’s migration issue.