Authorities in Croatia say 42 migrants have been hospitalized due to hypothermia and carbon monoxide poisoning after several dozen, including children, were found packed in a van traveling through the country.

Croatian police stopped a van late Saturday with 62 migrants from Afghanistan and Pakistan crammed inside, state broadcaster HRT reported.

A police interceptor patrolling the Belgrade-Zagreb highway noticed the overloaded vehicle trailing smoke at Novska, 120 kilometers east of the Croatian capital.

The driver fled into the fields and was still at large the next morning. Of the people inside, 42 had to be treated for fume inhalation and hypothermia.

After spending hours in the cargo area of the van, several migrants had lost consciousness due to carbon monoxide poisoning, Croatian emergency medical care head Grba Buljevic told HRT.

None were in a life-threatening condition, but that would have likely changed had their journey not been interrupted.

It is believed they entered Croatia via Serbia and were on their way towards Austria and Germany.

The incident is further confirmation that the so-called Balkan migration route is still active - nine months after a surge in migrants and refugees pushing to reach Western Europe prompted transit countries on it to close their borders.

Though the number of people has dropped significantly since 1 million migrants and refugees came to Europe in 2015, people smugglers are still in operation on the route.

The trip remains dangerous. In August 2015, 71 migrants suffocated in a lorry illegally transporting them through Austria. Earlier, 14 were killed by a train as they walked along a railway in Macedonia.