A powerful natural gas explosion badly damaged a Maryland office complex and shopping center Sunday morning, ripping away part of the facade and exposing twisted metal, authorities said. No injuries were reported in the thundering blast, which occurred at about 8 a.m. It came after authorities said they had evacuated the area around the complex because of a suspected early morning gas leak near the complex in Columbia, Maryland. Fire crews responded about an hour before the explosion because of a fire alarm that was upgraded to a report of a gas leak in the parking lot, officials said.