Police in Austria say the bodies of 71 people, believed to be migrants, were discovered in an abandoned lorry found near the Hungarian border on Thursday.
The victims included 59 men, eight women and four children who are thought to have been dead for about two days.
Police said the group appeared to be migrants from Syria and probably died after suffocating in the vehicle.
Three people, thought to be Bulgarian, have been arrested in Hungary. They are said to be the owner and drivers.