Federal safety investigators said Tuesday that natural gas leaked from a defective fitting at the Pennsylvania chocolate factory where seven people died after a massive explosion.

While the cause for the March 24 explosion continues to be under investigation, officials found that one of two leaks at the R.M. Palmer Co. plant in West Reading was fractured, according to the National Transportation Safety Board. In an investigative update, the board said the fractured fitting was installed in 1982 and that they determined a small leak on another fitting installed in 2021.

The 1982 fitting had a known tendency to crack and in 2007 was added to a federal government list of pipe materials with “poor performance histories,” according to the update. It remained connected to the natural gas system and was left in place during utility work two years ago.

The explosion leveled an entire building and heavily damaged another. Employees in both said they smelled gas before the blast, according to investigators. Workers at the plant accused Palmer of ignoring warnings of a natural gas leak stating that the plant should have been evacuated.

Attorney Robert Mongeluzzi has filed a lawsuit against Palmer and DuPoint, the company that made the older fitting as well as the chocolate factory’s natural gas utility UGI Corp. In a press release Tuesday, Mongeluzzi said the investigative update shows that the mass-casualty explosion was the result of “shoody materials and shoody work.”

“Today’s NTSB findings are disturbing. Natural gas is deadly and gas companies must protect the public from devastating explosions. The continued use of piping and materials known to be dangerously defective is outrageous,” Mongeluzzi said in the statement. “UGI’s conduct is inexcusable.”

Representatives for DuPoint and UGI told USA TODAY that they are aware of and reviewing the NTSB’s update and can not comment on the litigation surrounding the blast.