Three Syrian children and their families who were rescued from a minivan holding 26 refugees have disappeared from the hospital where there were being treated.

The children were suffering from severe dehydration when found by authorities and were taken to a hospital in the town of Braunau am Inn on Friday, the BBC reported Austrian police as saying.

The vehicle in which three migrant children, aged between 5 and 6 were saved by Austrian Police (EPA)

Austrian police said that they stopped the minivan in Braunau, which sits on the country’s border with Germany, on Friday and arrested its Romanian driver.

The children - two girls and a boy aged between one and five – were said to have been crammed in the back along with other migrants from Syria, Afghanistan and Bangladesh, according to reports.

Police said that they were critically ill and almost unconscious when found.

According to the BBC the children and their family all disappeared from the hospital at the same point on Saturday.

It is believed by authorities that they may have tried to cross the border into Germany, rather than face deportation back to Hungary

The disappearance comes after the deaths of 71 people, believed to be migrants, whose bodies were found in an abandoned refrigeration truck on a highway in Austria last week.

Police prepare to load a group of Afghan migrants into a van after the migrants crossed from Austria into Germany (Getty Images Europe)

A fifth suspect of Bulgarian citizenship was arrested today by Hungarian police in connection with the deaths.

Austrian police have said that they believe the migrants suffocated after autopsies were performed on 16 of the bodies.

Three Bulgarians and one Afghan citizen are currently under arrest pending an investigation in Hungary. They face up to 16 years in prison for trafficking in Hungary plays murder charges in Austria.

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The refrigerated truck in which bodies of 71 migrants were found on the A 4 Austrian highway (Vladimir Simicek/AFP/Getty Images)

French Foreign Minister Laurent Fabius slammed eastern European states, notably Hungary, on Sunday for having a “scandalous” policy towards refugees, which went against the values of the European Union.

Home Secretary Theresa May has said that Europe's borderless system was intensifying a migrant crisis.

The International Organization for Migration estimates that a third of a million people have crossed the Mediterranean so far this year, leaving Libya, Turkey and other countries to arrive in Europe.