A special effects stunt on the Hungarian set of A Good Day to Die Hard is said to have sparked the blaze, E! News reports.
An action sequence involving a helicopter and a building on fire went wrong when the blades of the helicopter reportedly escalated the fire, engulfing the entire structure. There were no injuries during the fire, which was extinguished quickly.
Willis and co-star Patrick Stewart were not present during the accident.
20th Century Fox executives have released a statement which reads: "There was a fire on the set of A Good Day to Die Hard in Hungary.
"No one was injured by the flames, which occurred during a pyrotechnics stunt just after midnight on Thursday (July 5), and were contained a short while later.
"Principal photography on the movie began in April in Budapest, and is expected to wrap late summer."
A Good Day to Die Hard, the fifth movie in the Die Hard franchise, is due for release in February 2013.
Photo gallery - 'A Good Day to Die Hard' filming: