Authorities say an explosion that injured two workers at a Minneapolis commercial building on Wednesday has been ruled accidental. The Minneapolis Fire Department responded at about 2:45 p.m. Wednesday to an explosion at Metal-Matic, located at 629 2nd St. SE. When firefighters arrived, they found two workers who had suffered significant injuries from the blast. Authorities say the two workers were hospitalized. The explosion caused a small fire, which crews were able to put out. Fire officials say the cause of the explosion has been determined to be accidental. It happened when a pipe welding torch ignited an aluminum dust and water mixture.