(Silver Spring, MD) — The National Transportation Safety Board says a failed gas vent caused the August 2016 explosion that destroyed two apartment buildings and killed seven people in Silver Spring, Maryland. NTSB officials said today that the failure allowed gas to build up inside a basement meter room until it encountered an ignition source that sparked the blast at the Flower Branch Apartments. Investigators say the vent was owned by Washington Gas and was its responsibility. Residents at the garden-style apartment complex had reported smelling natural gas in the weeks before the explosion. Dozens were injured in the incident.