The Associated Press reported that the group, which claimed Massey artificially inflated its stock prices from 2008 to 2010, said in a motion requesting the federal suit’s deadlines be waived that it would not be ready for the June 7 hearing because of a lack of access to evidence.

The shareholders said in the documentation that the evidence needed was still not available to them because of the US Attorney’s Office criminal probe of the April 2010 UBB mine explosion that killed 29 miners.

The group, headed by the Massachusetts Pension Reserves Investment Trust, told the AP that they were in talks with the USAO to gain access to a portion of the needed evidence, but added in the request to US District Judge Irene Berger that more time was needed to lay out the details of that deal.

The hearing date went on following the rejection of a motion for the case’s dismissal in April.

Assistant US Attorney Steve Ruby, the lead prosecutor for the UBB investigation, told the news service the agency was attempting to determine a process to allow the progression of the civil case while not impacting its own probe.

“We haven't said no,” he said adding that, by the end of June, “we'll either work it out or know that we can't work it out”

While the criminal side of the UBB investigation was ongoing, the USAO had not recently commented on its status to media outlets. Ruby also declined comment on the topic to the AP.

Massey was acquired by Alpha Natural Resources in June 2011. The Virginia-based producer announced in April that it would close the UBB mine in Raleigh County permanently.

The investors initially filed the lawsuit in April 2010, less than a month after the explosion, and named Alpha Appalachia Holdings and Massey officials including former chief executive Don Blankenship, claiming violations of the Securities Exchange Act of 1934.

“Safety at Massey's mines was repeatedly sacrificed so that aggressive production goals could be met,” the group alleged in the suit documentation.

“Massey had received numerous undisclosed citations arising from serious uncorrected safety and other regulatory violations at surface and underground coal mines it operates in West Virginia and neighboring states.”

According to federal records, the now-closed UBB mine was shut down by the US Mine Safety and Health Administration 48 times in 2009 alone but abatements of the violations allowed the operation to reopen shortly after.

From the beginning of 2009 until the day of the UBB mine explosion that killed 29 workers on April 5, 2010, MSHA issued 645 violations to Massey with $US1.2 million in penalties. However, the investors were not made aware of them.