JOSH KOVNER and DAVE ALTIMAN, The Hartford Courant

MIDDLETOWN, Conn. -- Investigators are focusing on a welder's torch as the possible cause of Sunday's deadly blast at the Kleen Energy Power Plant, sources said.

The explosion that killed five and injured more than a dozen occurred immediately after the purging, or cleaning, of the underground, natural-gas pipeline that runs about 800 to 1,000 feet through the Kleen Energy plant.

Sources familiar with the investigation and with the purging operation said that welding work wasn't entirely halted during or immediately after the purging Sunday morning. This operation can result in an accumulation of natural gas that must be vented from rooms and enclosures before other ignition sources, such as a welder's blow torch, can be safely introduced, experts said.

Fran Walters, of Florissant, Mo., wife of Chris Walters, a safety manager who died in the blast, said that a police officer told her, "'The building was full of gas and before they could do anything, it was too late.'"

Several sources said a purge was conducted Saturday without incident.

The plant was 96 percent complete and was being readied for a summer opening.

The blast Sunday blew a construction trailer 40 feet into the air and was heard and felt for miles. Several sources said there were also industrial space heaters inside the otherwise heatless building.

"Why have people inside the building when doing this test?" U.S. Rep. Joe Courtney, D-Conn., said Monday. "You're just asking for trouble."

Courtney visited the blast scene Monday, just as state personnel were preparing to remove some of the bodies from the area. He said members of trade unions who had gathered at the site were allowed to escort their fallen brothers out of a ravaged power-plant building for the last time.

"They moved in while we were getting briefed. It was such a moving scene. It hurt literally just seeing it," Courtney said.

State and Middletown police have control of the site and have a warrant to search the area and seize evidence. Courtney said officials were treating the plant as a crime scene for the purpose of limiting access to the blast area as the search for the cause and origin of the blast proceeds.

"The big thing is to be able to tell the families what the hell happened out there," said one official.

Lawyers representing the Kleen Energy plant had told state regulators in a Jan. 15 letter that the official opening of the plant, or the "commercial operation date," was Nov. 30, 2010. But the letter, by lawyers from Pullman & Comley to the Connecticut Siting Council, went on to say that project officials were estimating that the plant would be open by this summer.

New London, Conn., attorney Robert Reardon, who is representing one of the injured pipe-fitters, said subcontractors had been working seven days a week recently to meet a late spring, early summer deadline.

"They were under tremendous pressure to get the plant finished," Reardon said Monday. "There was a rush to finish, and they were told, 'We have to get this done.'"

A separate state inquiry will focus on worker safety and other labor, training, permitting, and supervision issues at the site, Gov. M. Jodi Rell announced Monday.

Deputy Middletown Fire Marshal Al Santostefano said the main investigation -- being conducted by multiple city, state, and federal agencies, including the U.S. Occupational Safety and Health Administration and the U.S. Bureau of Alcohol, Tobacco, Firearms, and Explosives -- will explore whether other ignition sources were present during and after the purging.

"It's going to try to determine whether all electricity was shut down as a precaution, workers moved from the area -- all of those issues," Santostefano said.

Inspectors with the U.S. Chemical Safety Board will be looking closely at whether the purging of natural gas contributed to the explosion. The inspectors, who are civilians, were initially barred from the scene, but Santostefano said Tuesday evening that they are now part of the investigation.

"Reports indicate that this may have involved gas purging," said spokesman Daniel Horowitz said. "This is an issue the board is very concerned about."

The board, an independent federal agency, recently issued safety recommendations concerning purging after investigating the natural-gas explosion in June 2009 at the ConAgra Slim Jim production facility in Garner, N.C., which caused four deaths, three critical life-threatening burn injuries, and other injuries that sent a total of 67 people to the hospital.

One key recommendation was that purging operations should be conducted in a way that avoids a buildup of natural gas, and that the gas must be vented and be fully dissipated before the area is safe, according to a Feb. 4 news release from the chemical safety board.

O&G Industries of Torrington, Conn., is the general contractor building the plant, and principal David Oneglia is also a partner in the ownership of the plant.

In November, O&G paid a $1,000 fine for not meeting standards for recording and reporting occupational injuries and illnesses, according to OSHA records. The violation is in the least serious category of violations, an OSHA spokesman said.

The Middletown explosion is the most serious incident of its type in the United States in at least a year, Horowitz said.

William Corvo, a principal partner in the Kleen Energy project, declined Tuesday to answer questions about safety protocols or provide details of the purging operation.

"We're focused now on the human side," said Corvo, who was the face of the project in Middletown and in Connecticut during the seven-year process to win permits, capacity contracts, and about $1 billion in financing. "We have people who were hurt, people who were killed. We're worried about the families."

Kleen Energy's natural-gas line connects to the Algonquin pipeline's meter station at the base of the power-plant site. The Algonquin line is part of a national gas-transmission system. The utility extended its local line about 1.5 miles and constructed the meter station to accommodate the project, said Algonquin spokeswoman Toni Beck.

"We introduced natural gas to the lateral and to the meter station in November," said Beck. "Since then, Kleen Energy was taking flows as they commissioned the plant."

She declined to say how much natural gas the plant was using.

Meanwhile, Congress plans to hold a hearing on the Kleen Energy explosion.

U.S. Reps Courtney, Rosa DeLauro, and John Larson, all Connecticut Democrats, said in a statement Monday afternoon that they have received a commitment for a hearing from House Education and Labor Committee Chairman George Miller, D-Calif. They made the request after surveying the blast scene.

Courtney said it was "imperative that we review what went wrong and to make sure that all appropriate measures are put in place to prevent this type of catastrophe from happening again."

Rell on Tuesday said she is assembling a panel of state agencies -- to be chaired by Senior U.S. District Judge Alan H. Nevas -- "to identify the cause and origin of the Kleen Energy power plant explosion in Middletown on Sunday, including any potential contributing factors" such as construction problems, worker-safety issues, the adequacy of the on-site supervision, and issues of training, licensing, and permitting."

Rell said a second group of state agencies, local officials and experts will review the disaster and the findings of the Nevas-led panel and other investigations. The second panel will determine whether any changes should be made to Connecticut laws, state and local regulations or building and fire codes to protect both workers and residents living in the areas surrounding construction projects.

"Our response to the Middletown explosion must follow two distinct but critical paths," Rell said in a statement. "We must first identify what went wrong and then determine every measure we can take to prevent future catastrophes. The reviews must be thorough, impartial and swift.

And if there are concrete steps we can take in the meantime, we must be equally swift in putting those new measures into place."

(Courant staff writers David Owens, Daniela Altimari and Ken Gosselin contributed to this story.)

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