Northern Irish referee Arnold Hunter was left badly shaken after being struck by an object from the crowd during a Europa League game in Romania.
Arnold Hunter, who officiates in the Northern Ireland Football League, had to be treated on the pitch and was unable to finish the remaining few minutes of the match between Universitatea Craiova and Budapest Honved.
A flare thrown from the stands landed close to Hunter before he was struck by the object, reported to be a lighter. The incidents happened after a brawl between the players.
An ambulance was driven across the pitch so paramedics could attend the referee.
The match was suspended for more than 30 minutes before the final stages of the 0-0 draw, and subsequent penalty shoot-out, were played with the fourth official in charge, with Universitatea Craiova winning 3-1 on penalties.
The website of visiting side Budapest Honved described the scenes as "unacceptable" and "scandalous," and said the game should have been called off.
UEFA will wait for the referee report before deciding on the best course of action.