It's possible that some fires that had no causes were tests for Directed Energy Weapons. I do believe that the Minneapolis Bridge was taken down by a Directed Energy Weapon using sound, because of a Scorcha Faal report that says that a Russian Research Center has scientific evidence of an ultra low frequency blast. A building that is involved in research of such weaponry is Augsburg College, which is right by the bridge. The bridge was probably taken down in a test of this experimental type of DEW, which uses sound. Augsburg College, which researches this type of weaponry, was probably where the Directed Energy Weapon was tested and where it was hidden. A structural engineer is on the record saying that it was very 'unusual' how the bridge came down at both ends. It came down so fast, and for a collapse, a lot of the bridge was sure turned to dust. There's been a witness report of a man who saw a 100-200ft smoke plume..This is similar to how the twin towers were reduced to dust with a Directed Energy Weapon. Though, this particular witness saw something that fits like a glove with a Directed Energy Weapon. He says that he saw a huge blast, but no loud explosion. A soundless blast. This is completely consistent with a Directed Energy Weapon.
Another possible Directed Energy Weapons test is the NYC pipe blast. The smoke seemed to be 'pushing up' with force, and the bus right by the blast seemed to be completely undamaged. Some people were burnt.