A battle among Arch Coal Inc. creditors is intensifying as the miner prepares for a potential bankruptcy filing.

A group of middle-tier bondholders hired law firm Brown Rudnick LLP to help protect their investments as the miner moves toward restructuring its $5.1 billion of debt in court proceedings, according to a person with knowledge of the matter. The hiring comes after Arch, the largest coal miner in the U.S. by volume after Peabody Energy Corp., said in a filing earlier this month that it was in talks with creditors on a “significant restructuring” of its balance sheet and it may file for Chapter 11 protection regardless of whether it strikes a deal with creditors.

More at Bloomberg