Federal prosecutors want a judge to continue delaying a lawsuit by investors who say Massey Energy lied about its safety record to inflate stock prices before the Upper Big Branch mine disaster.
U.S. District Judge Irene Berger will hear the arguments privately Thursday in Beckley.
U.S. Attorney Booth Goodwin says he needs to protect the integrity of evidence gathered in the continuing criminal probe of the 2010 disaster that killed 29 men.
He says sharing evidence now would reveal the status and direction of his criminal investigation.
Goodwin says that could, at worst, allow potential defendants to shape their own statements or obstruct justice by influencing the testimony of others.
A previous order to delay the investors' case expired last week.
Goodwin wants a new extension until July 15.