A thunderous explosion Tuesday at a nursing home just outside Philadelphia killed at least two people, collapsed part of the building, sent fire shooting out, and left people trapped inside, authorities said. Pennsylvania Gov. Josh Shapiro said in a news conference several hours after the explosion that at least two had been killed after emergency responders braved the flames, a heavy odor of gas, and a second explosion to evacuate residents and employees, the AP reports. Fire officials said they were in "rescue mode" five hours later, with responders still digging by hand and using search dogs, earth-moving equipment, and sonar to locate potential victims. The explosion happened at Bristol Health & Rehab Center in Bristol Township, just as a utility crew had been on site looking for a gas leak.