More than 70 bodies, thought to be migrants, were in an abandoned lorry found on a motorway.
They originally estimated that between 20 to 50 people died in the vehicle, found near the Hungarian border.
Police discovered the decomposing bodies on Thursday morning after being sent to investigate the dumped lorry on the A4 motorway heading towards Vienna.
The local police chief said it appeared those in the vehicle had been dead for one and a half to two days.
The victims were probably already dead when the vehicle crossed into Austria from Hungary, authorities said.