The Austrian authorities discovered two dead refugees in a van on the border with Hungary.
The police told the AFP news agency on Tuesday that when the vehicle was checked, the officials found almost 30 people crammed into a confined space, two of them dead. The surviving migrants, most of whom come from Syria, were supplied with water.
The police were looking for the fugitive driver.
"This terrible act shows one thing clearly: the death of one or more people is deliberately accepted by smugglers," said Austria's Interior Minister Karl Nehammer.
The government in Vienna had tightened controls at the eastern and southern national borders in July due to increasing arrivals of migrants.
According to the police, 250 people smugglers have been arrested since the beginning of the year.
In August 2015, the suffocation of 71 people crammed into a truck in Austria caused international outrage.
Most of the victims, including four children, came from Syria, Iraq and Afghanistan.
Almost four years later, Hungarian courts sentenced the smugglers to life imprisonment.