GRAND FORKS, N.D. (KFGO) – A massive fire last Tuesday night at the 3G Ventures warehouse on the north side of Grand Forks has been classified as undetermined.The fire marshal’s investigation was hampered by the dangerous structural condition of the 10,000 square foot building and the excessive amount of damage.High definition images of the building were taken with a drone but the exact cause of the fire could not be pinpointed.The warehouse stored computer servers.The fire marshal’s report says one possible cause was the failure of electrical equipment being used in the building.