Austrian police have said 71 refugees including 59 men, 8 women and 4 children lost their lives inside a refrigeration truck abandoned on a motorway near Vienna.

The driver of a lorry dumped by the side of a road in Austria with the bodies of 71 refugees inside has been arrested, Hungarian police said on Friday, amid indications that those trapped in the vehicle, including four children, had suffocated to death.

Austrian police have confirmed that a total of 71 people – 59 men, eight women and four children, the youngest a one-year-old girl – suffocated after being abandoned on Wednesday in a truck on a motorway near Vienna.

At a press conference, Austrian authorities said they believed the victims were Syrian refugees and confirmed Hungarian police had arrested seven men and still had three in custody, two Bulgarian nationals and one carrying a Hungarian ID card.

“We are fairly confident that . . . they are part of a Hungarian-Bulgarian trafficking ring,” said Mr Hans-Peter Doskozil of the Austrian police.

While an examination of the vehicle was ongoing, he said it was “quite likely that the people suffocated in the truck”.

Given the 3,000 trucks that travel the A4 motorway each day between Hungary and Austria, police say it is not possible to do anything but spot checks on what they admit is an “intensively-used trafficking route”.

Austrian interior minister Johanna Mikl-Leitner praised the rapid arrests as proof of effective cross-border police cooperation.

She said it was important that EU member states find legal ways for refugees to leave warzones for Europe. She also called on the EU to help refugees remain in their homes by tackling at their roots the causes of the refugee crisis.

She also called for greater international cooperation and a “zero tolerance approach to trafficking”.

“Austria does not plan to impose strict border controls, what we are doing are border area controls,” she said.

“I take a dim view of [inner EU] border controls, it’s far more important to secure the outer EU border and to set up secure reception centres where we can differentiate quickly between war refugees and migrants for economic reasons.”

Police suspect the refugees in the back of the seven-and-half tonne truck were already dead as they were driven into Austria as early as Tuesday.

Romanian traffickers are suspected of being behind the tragedy, after abandoning the truck with Hungarian licence plates on the A4 motorway near the Hungarian border and 50km from Vienna.

The motorway is a popular overland route for traffickers bringing refugees from the Balkans into central and northern Europe.

The truck was discovered at 11.30am on Thursday by a passing patrol car. The officers said it was impossible to give an initial estimate of the victims, or their origin, because the bodies were already in an advanced state of decomposition.

“The officer who arrived noticed the truck was dripping,” said Mr Doskozil. “We can gather that death occurred sometime before . . . but this point we can offer no further concrete details as to how the death occurred.”

German chancellor Angela Merkel, attending a conference in nearby Vienna, said she was “shaken” by a tragedy which showed how urgently the European Union needed a new agreement for a fairer distribution of refugees across member states.

“We have more refugees in the world than at any time since World War II,” she said. “The eyes of the world are upon us.”