Natural gas leaked from a defective fitting at a Pennsylvania chocolate factory where a powerful explosion leveled one building, heavily damaged another and killed seven people, federal safety investigators said Tuesday as they continued to investigate the cause of the blast.

One of two leaks at the R.M. Palmer Co. plant in West Reading was traced to a gas fitting that was installed in 1982 and was determined to have fractured, according to an investigative update released by the National Transportation Safety Board. Investigators also determined there was a small leak on a natural gas fitting installed in 2021, the board said.

The older fitting, made by DuPont, had a known tendency to crack, and it was added to a federal government list of pipe materials with “poor performance histories” in 2007, the safety board said. But it was left in place during utility work two years ago and remained connected to the natural gas system.

The findings outraged lawyers for the victims’ families.

“It’s one thing to lose a family member because of some unforeseen, unknown hazard,” said attorney Robert Mongeluzzi, who has filed suit against Palmer, DuPont and UGI Corp., the natural gas utility that served the chocolate factory. “But here, this was a problem and a defect that has been known for decades, and that makes the loss and the tragedy even worse.”

About 70 Palmer production workers and 35 office staff were working in two adjacent buildings at the time of the March 24 blast. Employees in both buildings told federal investigators they could smell gas before the explosion. Workers at the plant have accused Palmer of ignoring warnings of a natural gas leak, saying the plant, in a small town 60 miles (96 kilometers) northwest of Philadelphia, should have been evacuated.

UGI, which provided natural gas to the factory complex via two mains, has said there wasn’t any utility work going on in the area, and that it detected no sudden surge in gas usage before the explosion.

Safety investigators determined that UGI replaced a service line at the Palmer plant in 2021, but kept the 1982 service tee connected to the system and fully pressurized.

“We have reason to believe that UGI was very well aware of the dangerous, defective problems with the DuPont piping, yet left that DuPont piping in place in 2021,” said attorney Andrew Duffy, who works with Mongeluzzi to represent survivors and families of victims. Noting the safety board also found a leak in the new piping, he added: “Seven people lost their lives due to shoddy materials and shoddy work.”

Civil litigation filed after the Palmer blast said older plastic pipe manufactured by DuPont and others has long been linked to failures around the country. Federal regulators said as far back as 1998 that much of the plastic pipe manufactured for natural gas service from the 1960s through the early 1980s was susceptible to cracking.

Investigators said they are looking at the gas leaks as a possible cause or contributor of the chocolate factory blast, but have made no conclusions.

“We are not at a point to say what caused the explosion,” NTSB spokesperson Keith Holloway said Tuesday.

The cracked fitting was less than two feet from other pipelines that ran between the two plant buildings, including a steam line, a condensate line and several pipelines filled with heated chocolate. Investigators said they also saw a crack in the steam line.

UGI said it’s aware of the safety board report and is cooperating. The utility declined further comment on an ongoing investigation. “Our focus and commitment remains with the victims and the West Reading community,” said utility spokesperson Joe Swope.

Palmer said in a statement that it remains focused on rebuilding and “doing all we can to help the entire West Reading community recover.” DuPont said it was reviewing the safety board’s report but declined further comment, citing the civil litigation.