Hungary said it would join the investigation into the discovery Thursday of between 20 and 50 dead migrants on a truck in Austria after it emerged the vehicle had Hungarian number plates.

"Austrian and Hungarian police will work closely together to take the necessary steps to investigate what happened and apprehend those responsible," Prime Minister Viktor Orban's spokesman Janos Lazar said, adding that Hungary had been informed by Austrian police that the driver was Romanian.

"It appears that the victims were illegal migrants in a human trafficking operation."