Gas blast at power plant kills at least 5

? An explosion that sounded like a sonic boom blew out walls of an unfinished power plant and set off a fire during a test of natural gas lines Sunday, killing at least five workers and injuring a dozen or more.

The explosion at the Kleen Energy Systems plant in Middletown, about 20 miles south of Hartford, could be heard and felt for miles.

Deputy Fire Marshal Al Santostefano told The Associated Press on Sunday night that no one was known to be missing amid the rubble from the damaged plant. Still, crews planned to spend all night going through debris in case there were any more victims. The cause of the gas explosion was unknown, and the investigation was to begin this morning, he said.

The explosion left huge pieces of metal that once encased the plant peeling off its sides. A large swath of the structure was blackened and surrounded by debris, but the building, its roof and its two smokestacks were still standing.