MIDDLETOWN, Conn. (AP) — An explosion blew apart a power plant under construction as workers purged natural gas lines Sunday, killing at least five people and injuring a dozen or more in a blast that shook homes for miles. At least 12 people were injured in the explosion at the Kleen Energy Systems plant in Middletown, about 20 miles south of Hartford. Crews with dogs were still searching the rubble for survivors as darkness fell over the plant, overlooking the Connecticut River.