West Virginia US district judge Irene Berger recently signed an order that will put the suit, which has been open since 2010, on hold for six months to allow involved parties to retain outside assistance.

The investors initially filed the lawsuit in April 2010, less than a month after the Upper Big Branch mine explosion on April 5.

They named Alpha Appalachia Holdings and Massey officials, including former chairman and CEO Don Blankenship, claiming violations of the Securities Exchange Act of 1934.

The group, headed by the Massachusetts Pension Reserves Investment Trust, claimed Massey artificially inflated its stock prices from 2008 to 2010.

“Safety at Massey's mines was repeatedly sacrificed so that aggressive production goals could be met,” the group alleged in suit documentation in 2012.

“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 the Associated Press, all parties have stated in court filings that efforts to settle the case have been ongoing since a face-to-face meeting in December 2011.

Written communications followed, including “a series of demands and counter-offers that have narrowed the extent of the disagreement”

As a result, the joint motion filed earlier this month indicates the talks have reached a juncture where mediation would be of help.

The case had previously been on hold because Berger was shielding some evidence from the group of investors. That evidence is part of an ongoing criminal investigation into the company following the blast that killed 29 workers.

Several investigations into the incident have been conducted in the years since, with many agreeing on the contributory factor that the explosion was caused by worn and broken equipment and exacerbated by methane and coal dust accumulations.

Falsification of safety records has also been uncovered in the time since the blast. Former superintendent Gary May and security head Hughie Stover have been incarcerated for their actions.

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, MSHA issued 645 violations to Massey with $1.2 million in penalties.

However, the investors were not made aware of them.

Massey was acquired by Alpha Natural Resources in June 2011.

The Virginia-based producer announced the following April that it would close the UBB mine in Raleigh County permanently.