The Mine Workers (UMWA) union and families of victims killed in the Upper Big Branch Mine disaster have filed suit in federal court to open to the public interviews of safety officials and others now being conducted behind closed doors by the Mine Safety and Health Administration (MSHA), according to a blog post on the AFL-CIO’s website.

UMWA President Cecil Roberts says the union was reluctant to file the suit. But after MSHA rejected the request to open the interviews, “we have been left with no choice. We believe it is imperative for the families of the victims of this tragedy to be able to hear the evidence that will be gathered in these interviews for themselves. We also believe that the workers — who will have to go back to work in that mine — must be allowed to have their designated representative in the interviews, asking questions and hearing testimony firsthand,” according to the web post.

The Massey Energy mine, where 29 miners died in an April 5 explosion, was nonunion, but several miners have designated the UMWA as their representative, as federal regulations allow. MSHA says the hearings and many other parts of the investigation will be open and transparent. But as Roberts says:

“The interview process is perhaps the most critical step in the entire investigation. That is where those with fresh, first-hand knowledge of what the conditions were in the mine will be asked to tell investigators what they know.”

Roberts said he had confidence that MSHA and the federal government want to determine the cause of the disaster and identify those who bear responsibility for it. “I know President Obama, [Labor] Secretary [Hilda] Solis and Assistant Secretary [Joseph] Main all have that goal. But the process that’s going to be used to get there is flawed and may not result in meeting that goal.”

The challenge was filed Monday of this week in the U.S. District Court of the Southern District of West Virginia at Charleston.

On May 18, AFL-CIO President Richard Trumka will join UMWA and other union members in a march and rally at Massey’s annual shareholders meeting in Richmond, Va. They will demand that Massey — with its long history of safety violations at Upper Big Branch and other mines — be held accountable and that Massey CEO Donald Blankenship step down, according to the AFL-CIO blog.