Pennsylvania utility regulators must turn over inspection records to the National Transportation Safety Board as part of the federal agency's probe into a fatal explosion at a chocolate factory last year, a federal judge ruled this week.

U.S. District Judge Christopher C. Conner sided Tuesday with the federal safety board in its dispute with the Pennsylvania Public Utility Commission, which had refused to produce inspection and investigation reports for UGI Utilities Inc.

UGI is a natural gas utility at the center of the probe into the March 24, 2023, blast at the R.M. Palmer Co. plant in West Reading. The powerful natural gas explosion leveled one building, heavily damaged another and killed seven people. Investigators have previously said they are looking at a pair of gas leaks as a possible cause of or contributor to the blast.

State utility regulators had spurned the federal agency's request for five years' worth of UGI inspection records, citing a state law that protects "confidential security information" about key utility infrastructure from public disclosure, even to other government agencies.

The utility commission offered federal investigators a chance to inspect the reports at its Harrisburg office or to sign a nondisclosure agreement, but the safety board refused and then issued a subpoena.

The safety board said the records are vital to its investigation because they include state utility regulators' assessment of the condition of UGI's pipelines, as well as leak or odor complaint investigation records for the gas utility. The agency argued that federal regulations entitled it to the state investigation records.

"These reports are also vital to determine whether the commission conducted oversight of UGI's pipeline system in compliance with federal regulations," federal prosecutors, representing the safety board, wrote in their March 29 petition asking the court to enforce the subpoena.

In its response, the state agency pointed out that federal investigators had already obtained some of the requested records from UGI itself, and argued in a legal filing that federal law does not automatically preempt conflicting state laws.

Conner gave utility regulators seven days to produce the subpoenaed documents, but said they could do it in a way that complies with state law.

"From the beginning, the PUC has underscored a commitment to assist the NTSB with this investigation -- while also complying with the Commission's legal obligation to safeguard confidential security information," said Nils Hagen-Frederiksen, a spokesperson for the utility commission.

He said the judge's decision was made as a result of discussions between the two agencies.

An NSTB spokesperson declined comment. The federal investigation into the blast is ongoing.

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

Palmer was fined more than $44,000 by the U.S. Occupational Safety and Health Administration for failing to evacuate. Palmer denied it violated any workplace safety standards and contested the OSHA citations.