Piotr Walkowicz from the prosecutor's office in Stalowa Wola said: "On the straight section of the road they tried to overtake another car. It was clear and dry that day. We do not know yet why the driver, during the overtaking manoeuvre, came off the side of the road."
The pair hit a concrete sign then a tree. It is believed they were killed instantly.
Other drivers called emergency services and police, ambulance and fire crews were in attendance but it was too late.
Investigating officers say there was "no chance" of the pair being rescued.
Mr Walkowicz continued: "The car was scrap metal. And the injuries of these men were simply unimaginable. I still have the picture in front of my eyes."
Local media said other guests attended the scene to pick up the rings and the wedding went ahead.
An investigation has been opened into the incident.
Tributes have since been paid to the pair who died.
An unnamed teacher from the high school both men had attended said: "They were the most positive, kind and nice people you can imagine. I can not even mourn them both, it is surreal for me that they are even gone."
- australscope