Justice authorities from the canton have launched an investigation into criminal homicide by negligence in the death of the 56-year-old man near St. Margrethen late last month.
The victim, a Serb living in Switzerland, got out of his car after it was struck by another vehicle at 5.30am on October 25, according to cantonal police information.
He was subsequently struck by another car whose driver stopped a few hundred metres along the road to inform police.
A further 16 vehicles ran over his body, including several vans and trucks, cantonal police said.
Police have tracked down the drivers of the first vehicles to drive over the man after appealing through the media for more information.
Among them was the driver of a van who lost a wheel cover near the scene of the tragedy.
The driver told investigators he thought he struck an animal or an object.
In addition to criminal negligence, the public prosecutor is also looking at violation of the responsibilities in dealing with a motor vehicle accident.