The Europa League game between Dudelange and Azerbaijani club Qarabag had to be briefly suspended in the first half Thursday after a drone flew over the field carrying what looked like an Armenian flag.
The drone incensed Qarabag players, who tried to hit it with the ball as it flew over the center circle, and the referee made the decision to halt play for more than 20 minutes with Qarabag leading 2-0.
Play later resumed, with Qarabag winning 4-1.
UEFA said the decision to halt the match was taken "for safety and security reasons."
"UEFA will await the official reports from the match officials to determine whether disciplinary proceedings will be opened," the European governing body said in a statement.
Azerbaijan and Armenia are in a territorial dispute over the Nagorno-Karabakh region. A fan carrying the Armenian flag also ran onto the pitch during Qarabag's away game at Arsenal in London in last season's Europa League.
Nagorno-Karabakh is a region of Azerbaijan which has been under the control of ethnic Armenian forces backed by Armenia since a war there ended in 1994.