The two girls and one boy aged 5 and 6 had been in a dire state when police stopped the van after a high-speed chase close to the town of St.
Peter am Hart on the border with Germany, a spokesman for Austrian police said. They are now recovering in hospital.
“The emergency doctor told us they would not have made it much longer – two, maybe three hours,” said David Furtner, police spokesman for Upper Austria province.
“The driver did not give a damn about the people in the back. We would not transport animals under these conditions on our roads in Austria.”
The incident follows the discovery of the corpses of 71 refugees in an abandoned truck on an Austrian highway on Thursday, victims of an unfolding tragedy as refugees and migrants fleeing conflict and poverty in Africa, Asia and the Middle East flock to Europe in unprecedented numbers this year.
Austria lies on the way from poor countries in east Europe where many refugees first land to more prosperous nations, notably Germany and Britain.
The 29-year-old Romanian driver of the van found on Friday, registered in Romania, was arrested. The children and their parents were taken to the hospital in Braunau, where they are now in a stable condition.
Four children, including a baby girl, were among the dead, presumed to be from Syria and possibly Afghanistan, who were found in the truck on Thursday. Police said on Saturday they were hoping to help identify the dead refugees by examining mobile phones found on some of the bodies.
Searches of backpacks, luggage and clothing had provided few clues apart from one Syrian travel document, said Helmut Marban, police spokesman in the province of Burgenland.
“We will examine the phones and this will maybe lead us to the identity of the people,” said Marban. “We hope we will soon get results.”
He was speaking in front of a former customs hall where the truck was standing on tarpaulin to gather fluids, with investigators clad in protective suits gathering forensic evidence.
Police estimated the refugees could have been dead for up to two days and the truck might have been standing on the hard shoulder of the highway for as long as 24 hours.
“It seems unbelievable,” said Marban, asked about how 71 people could have fitted into the medium-sized refrigeration truck.
“At first when they got in they were of course standing, but when we had to bring them out they were (entangled) altogether.”
In nearby camps, refugees said the news had left them stunned, but they had seen little choice but to flee to Europe.
“We had to walk so much, it was so dangerous, in the forest and in the water,” said 21-year-old Qariburahman, who had been on the road for a month before Austrian police picked him up and brought him to the Nickelsdorf refugee reception center.
“When I came from Afghanistan, about three people died on the way, the way is very dangerous,” he said, adding his journey had cost him $5,000.
A Syrian refugee in the camp of Traiskirchen south of Vienna said people had no choice but go along with traffickers.
“We didn’t know what the car was, maybe it’s a truck, maybe it’s a van. And we had to follow (the trafficker) because in his area, he is the boss,” he said, his pregnant wife and baby son close by.
“My wife, she told me, ‘Oh maybe we were supposed to be one of them’… Maybe it is one of my friends, maybe it is one of my brothers on that truck.'”
Three Bulgarians and an Afghan arrested in Hungary in connection with the deaths made their first appearance in court on Saturday. The judge ordered them to be detained for one month for questioning.