A massive gas explosion ripped through a Connecticut-based power plant yesterday morning as workers cleaned a piping system, killing at least five and injuring many more. “Homeowners miles away said the explosion, reported shortly after 11 a.m. at the Kleen Energy Systems power plant under construction on River Road, created a shock wave so intense that some mistakenly thought the central part of the state had experienced an earthquake. A team of investigators from the federal government's Chemical Safety Board, charged with investigating industrial chemical accidents, was scheduled to arrive at the plant today. A board spokesman said the team will look for the cause of the explosion, with particular emphasis on the procedure used at the Kleen Energy plant to purge, or clear, the gas piping system. The identities of those killed were not being released Sunday night, but family members confirmed the death of Raymond E. Dobratz, 58, a pipefitter from Old Saybrook. ‘I lost my father today,’ said his son, David Dobratz, 32…Rescue officers worked throughout the day to prepare a casualty list, but the task was complicated by uncertainty over the number of workers on the site Sunday.”