VICKI SMITHMORGANTOWN, W.Va. (AP) â¿¿ The new owner of the West Virginia coal mine where 29 men died in an explosion two years ago on Thursday announced it will soon begin work to permanently seal the underground mine with concrete and finish the job by summer. Virginia-based Alpha Natural Resources, which acquired the mine when it bought Massey Energy last summer, said late Wednesday it will seal the portals â¿¿ large tunnels miners use to get underground â¿¿ at the Upper Big Branch mine. Boreholes will be plugged and shafts that house the huge industrial fans meant to sweep bad air out of the mine will be capped to prevent any access. "Everyone still has vivid memories of the tragedy and the suffering the miners' families endured," Chief Executive Officer Kevin Crutchfield said Wednesday. "For all of us in the mining industry, it is a solemn reminder of why we must always put safety first in everything we do." Meanwhile, the mother and siblings of one of those killed on Wednesday sued former Massey Energy chief Don Blankenship and eight others they hold responsible in their lawsuit for the worst U.S. coal mining disaster in four decades. An explosion fueled by methane and coal dust ripped through the seven miles of underground corridors at the former Massey Energy mine on April 5, 2010. Starting at 3:01 p.m. on Thursday, West Virginians led by their governor are planning to observe a moment of silence to mark the second anniversary of the deadly blast. Pittsburgh attorney Bruce Stanley filed the suit against the former Massey executives and mine managers in Raleigh County Circuit Court for the family of fallen miner Edward Dean Jones, just before the two-year statute of limitations expired. The complaint alleges deliberate infliction of emotional distress and demands compensatory and punitive damages.