The badly damaged Sylmar building that housed an alternative-energy non-profit company, Rainbow of Hope, is now the focus of a workplace safety investigation after "a thunderous explosion" rocked the area on Tuesday.
Three people were sent to the hospital, two with life-threatening injuries, said a Los Angeles Fire Department spokesman. One of the victims lost his arm and leg.
One of the men injured in the blast, Tim Larson, is a relative of Tyson Larson, the green energy entrepreneur killed in June of 2010 in an explosion at another green energy business called Realm Industries of Simi Valley.
"We were outside in the shop and all of sudden, we heard just a loud explosion," said witness Cuah Beltran, who works across the street. "You could actually feel it in your body. It was tremendous. It was incredible."
Witness Dee Dee Tronson said she heard the explosion shortly after 4 p.m.
"We were just in our office and our whole building shook," Tronson said. "That's when we knew something was wrong. We thought it was an earthquake at first, but then it was just too weird."
The front doors of the building were blown off. A massive hole was left in the ceiling. Debris was scattered 30 yards in all directions.
The business is located at 12349 Gladstone Ave. (map). The property owner of the building tells NBC4 he's afraid the tenants were doing more than eco-friendly non-profit research.
Firefighters say workers at the business were extracting hydrogen from water, when the explosion happened.
"In the process of extracting the hydrogen extracting product from one vessel to another there was an explosion," said LA City Fire Captain Jaime Moore.