Sunday morning's blast at the Kleen Energy Systems plant in Middletown, about 20 miles south of Hartford,and injured a dozen or more others. It happened as workers were clearing gas lines of air, but the exact cause remained under investigation.
"I lost a couple of good friends up there," Michael Rosario, a business representative with the local Plumbers and Pipefitters union, said as he broke down crying Monday. "I'm just so sorry something like this happened. They're all great people. We're all brothers and sisters."
He added, "There's still a lot of unanswered questions."
Welders and other workers were at the site Monday, preparing to make it safer for emergency personnel, said Ed Reilly, president of the Greater Hartford-New Britain Building Trades Council.
Middletown Deputy Fire Marshal Al Santostefano said about five people remain unaccounted of the nearly 100 workers who were at the plant, citing conversations with contractors and labor union officials. It was unclear whether those workers are missing or haven't been contacted yet by authorities.
Investigators returned to the scene Monday to try to begin determining the cause.
Santostefano said he didn't know when rescue crews would be able to search the small section of the plant that is unstable.
Piles of rubble were 10 feet tall in some parts of the plant, and mounds of rubble and debris were everywhere, he said.
Gov. M. Jodi Rell said Monday morning that officials still haven't received rosters of workers who were at the plant Sunday.
"There are a number of contractors who do the work at the building," Rell told WTNH-TV. "Until we actually have a roster of the names of those individuals that are in each of those groups and who was working on Sunday, we need that before we can do anything else. ... We're still confirming the number of people."
The explosion was so powerful it alarmed residents who heard the boom and felt tremors in their homes miles away.
The blast 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 at the site, which is near Wesleyan University on a wooded and hilly 137-acre parcel of land overlooking the Connecticut River.
Rescue crews combed through the debris until about 2:30 a.m. Monday.
The U.S. Chemical Safety Board, a federal agency that investigates industrial chemical accidents, was mobilizing a team of workers from Colorado and hoped to have them on the scene by midday Monday, spokesman Daniel Horowitz said.
The nearly completed 620-megawatt plant is being built to produce energy primarily using natural gas, which accounts for about a fifth of the nation's electricity. Workers for the construction company, O&G Industries, were purging a gas line, clearing it of air, when the explosion occurred around 11:15 a.m. Sunday, Santostefano said.
Santostefano said workers were at the site Sunday because they were trying to get the plant open on time the opening was slated for sometime in the middle of 2010 but he added "It wasn't like they were working in a frenzy."
One of those killed was Raymond Dobratz, a 58-year-old plumber from Old Saybrook, said his son Erik Dobratz, who called the elder man "a great dad."
Lynn Hawley, of Hartland, Conn., said her 36-year-old son, Brian Hawley, is a pipefitter at the plant and broke his leg. She said he called her from his cell phone to say he was being rushed to a hospital.
"He really couldn't say what happened to him," she said. "He was in a lot of pain, and they got him into surgery as quickly as possible."
Hospital officials didn't immediately release the conditions of the other injured people, whose wounds ranged from minor to very serious.
The thundering blast shook houses for miles.
"I felt the house shake," Middletown resident Steve Clark said. "I thought a tree fell on the house."
Mayor Sebastian Giuliano said he heard it as he was leaving church.
"It felt almost like a sonic boom," he said.
Kleen Energy Systems LLC began construction on the plant in February 2008. It had signed a deal with Connecticut Light and Power for the electricity produced by the plant, and would be one of the biggest built in New England in the last few years.
The company is run by former City Councilman William Corvo. A message left at Corvo's home was not returned. Calls to Gordon Holk, general manager of Power Plant Management Services, which has a contract to manage the plant, also weren't returned.
Energy Investors Funds, a private equity fund that indirectly owns a majority share in the power plant, said it was cooperating with authorities.
Safety board investigators have done extensive work on the issue of gas line purging since an explosion last year at a Slim Jim factory in North Carolina killed four people. They've identified other explosions caused by workers who were unsafely venting gas lines inside buildings.