Coal miner Massey Energy Co , owner of the Upper Big Branch (UBB) mine where at least 25 miners died in a blast this week, said it was working to increase production at its other mines to mitigate losses at UBB.

In a filing with the U.S. Securities and Exchange Commission, the company said it would be able to bring a majority of UBB miners back to work at other mines.

Massey Energy, however, added that it may not be able to replace 100 percent of the planned UBB production for 2010.

The company had planned to ship about 1.6 million tons of metallurgical coal from the mine for the balance of the year, at an average price of $91.00 per ton.

The accident at the UBB mine in West Virginia was one of the deadliest at a U.S. coal mine in recent years. The mine, owned by Massey's Performance Coal subsidiary, is about 30 miles south of the state capital Charleston.

Massey Energy said in the filing that it had third-party insurance coverage that applies to litigation risk.

We believe this coverage will apply to litigation that may stem from the UBB explosion.

The UBB mine has had three fatalities since 1998 and has a worse-than-average injury rate over the last 10 years, according to federal records.

Massey, headquartered in Richmond, Virginia, is the largest coal producer in Central Appalachia with operations in West Virginia, Kentucky and Virginia.

Shares of the company were up marginally at $46.25 in pre-market trade. The stock had closed at $46.14 Thursday on the New York Stock Exchange.

(Reporting by Adveith Nair in Bangalore; Editing by Maju Samuel)