Forensic examination results expected to establish how an Afghan migrant died near Bulgaria's border with Turkey last week are to be announced on Monday.

Police say a bullet that a border officer fired in the air as a warning sign rebounded off a bridge hitting a 25-year-old man who died from his wounds as emergency teams were fighting for his lie.

Thursday's incident is considered to be the first one reported at the EU's external borders since the migrant crisis began.

Human rights organizations have voiced outrage at the incident, while some Bulgarian politicians have suggested the police officer should be awarded a medal for carrying out his duty.

The expertise is aimed at finding out whether the death was indeed caused by a ricochet, as the Interior Ministry had suggested, or the border police officer shot directly at the man.

The incident occurred after police had tracked down a group of 54 people who had crossed into Bulgaria, possibly from Turkey, and were hiding under a bridge, reportedly to be collected by a smuggler and to continue their journey westwards.

Police suggest the group refused to follow their instructions and showed "resistance".

On Sunday authorities disclosed more information about the man's identity.