Thirty people were injured.
Prince Mohammed bin Fahd bin Abdulaziz, the governor of the eastern province where the incident occurred, ordered an immediate investigation into the incident, the Saudi daily Okaz reported Wednesday.
Hundreds were inside the courtyard of a home in the village of Ain Badr when the fire erupted, the BBC said.
Gunfire during the wedding reception Tuesday hit a high voltage power line that fell on a metal door, sending sparks that set off a fire.
The BBC said most of the casualties were said to be women although men and children were also hurt. They were taken to Aramco and Central Abaiq hospitals.
Last month Saudi Arabia banned the use of firearms at weddings, The (Lebanon) Daily Star said.