Probably a gas leak. Archive: https://archive.today/0W3sy From the post: >>The Denver Fire Department is investigating a fire that caused an explosion inside a building in Denver Wednesday morning. According to DFD, the fire broke out at a large nursing assisted living facility near Quebec Street and Smith Way around 11:30 a.m. Just after noon, an explosion was reported inside the building. Authorities said ten people are being evaluated for injuries, four of which have been taken for treatment.