The agency made the announcement late Tuesday, noting that the briefing coincides with the one-year anniversary of the date it began its underground investigation of the Raleigh County, West Virginia operation where 29 workers died.

“Although the underground investigation and interviews are still ongoing, MSHA investigators will be able to compile additional relevant evidence by June in order to provide a substantive presentation to the public,” officials said, noting that the briefing will be held at the National Mine Health and Safety Academy in nearby Beckley.

MSHA said it had shared its information to date with the families of the victims in several meetings.

At the June event, federal investigators will provide an overview of the physical evidence gathered in the investigation, along with summaries of other evidence obtained. Some of the information will remain confidential in light of the ongoing US Department of Justice probe as well as the agency’s requests to federal prosecutors to limit public release of evidence.

“We take very seriously the need to keep the public informed as to what we’re learning and when we’re learning it,” assistant secretary of labor for mine safety and health Joseph Main said.

“We also take seriously the efforts of the FBI and the US attorney to bring to justice those who may have broken the law. Throughout this investigation, we’ve worked hard to balance those important goals.”

The agency said it had conducted investigations for all of the approximately 4000 miner deaths that had occurred since the passage of the Federal Mine Safety and Health Act of 1977. The UBB probe and its 2006 investigation into the Sago explosion were two of the few where records were publicly released as the investigation commenced, despite its general practice to release records and information at the conclusion of an investigation.

“The Upper Big Branch mine investigation has been one of the most transparent in MSHA’s history,” the agency said.

“MSHA will continue to make publicly available relevant information that will not compromise MSHA’s investigation or the ongoing criminal investigation.”

UBB mine owner Massey Energy did not immediately respond to an ILN request for comment.