Kim West, NTSB Investigator-In-Charge, revealed that a retired gas line was the source of a leak that cause the factory to explode. "Staff found that natural gas migrated from the Aldyl A retired service tee, through the ground into Palmer's building two basement, then through the chocolate pipe conduits and into building one," West explained.

More than a year and a half after a candy factory exploded in West Reading, the National Transportation Safety Board finished its investigation. The NTSB presented its findings in Washington, D.C., on Tuesday.

About 70 production workers and 35 office staff at R.M. Palmer Co. were working in two adjacent buildings at the time of the blast.

A federal safety board says a corroded steam pipe and a defective natural gas fitting caused a powerful explosion at a Pennsylvania chocolate factory, killing seven workers when the company failed to evacuate.

NTSB holds a public hearing aimed at determining what the probable cause of the fatal explosion at the R.M. Palmer Co. chocolate plant was in March 2023.