WASHINGTON — A tight-knit community waited, watched and prayed late Monday night as rescue workers rushed to search for survivors of an explosion in a coal mine deep in the rugged hills of West Virginia.

Seven miners were confirmed dead and 19 were still unaccounted for hours after the fierce blast inside the Upper Big Branch mine between 3 and 3:30 p.m. The mine is owned by Massey Energy Co., one of the nation’s largest coal producers.

The explosion destroyed communication lines inside the huge mine. It wasn’t clear if the missing miners were able to reach specially reinforced rescue chambers that are stocked with food, water and air.

The mine, which comprises several square miles underground, has a history of releasing highly combustible methane gas, according to mine safety officials.

At least nine mine rescue teams and other emergency responders, as well as frightened families, converged on the rural mining town of Montcoal, which is about 30 miles south of Charleston, the state capital. Helicopters clattered overhead.

Elizabeth Pellegrin, a spokeswoman for the Charleston Area Medical Center, said one miner was flown in by helicopter at 6 p.m. The miner was in intensive care, she said, and doctors were preparing for other patients.

“”We’re hoping for more,”” Pellegrin said.

PresidentBarack Obamaoffered his condolences to those who lost loved ones in the disaster, according to the White House. The president spoke by phone Monday night with Gov.Joe Manchinand offered federal assistance in the rescue effort.

“”We are sending all of our prayers and thoughts to the brave miners and their families,”” said Sen.Jay Rockefeller, D-W.Va.

Massey Energy officials said they did not yet know the cause of the accident. The mine is operated by a Massey subsidiary, Performance Coal Co.

“”We’re uncertain as to what happened but we are working diligently on rescue efforts,”” said Massey Energy’s chief executive officer,Don Blankenship.

Kevin Stricklin, an administrator with the Mine Safety and Health Administration, told The Associated Press that the seven men apparently were killed while riding on a mine vehicle, and that two other men aboard the vehicle were injured.

He said the 19 missing include two crews of nine workers, and a fire boss who was working alone.

Two rescue chambers are situated near the blast site and are stocked with food, water and enough air to sustain the group for four days, Stricklin said.

He said officials don’t believe there was a roof collapse, but they don’t yet know what caused the explosion.

Jeff Gray, director of emergency services with the Central West Virginia Chapter of the American Red Cross, said officials were scrambling to get health and mental health services to the mine site.

“”It’s a very rural area,”” he said.

About seven miles from the mine, the First Baptist Church in Whitesville prepared sandwiches, hot dogs and soda for grieving families Monday evening, saidDennis Dye, a deacon with the church.

“”We’re prepared for them to come and we want them to come,”” he said.

Massey Energy says on its Web site that it has a safety record above the national average, with three fatalities at the mine in the last 12 years.

In 1998, a miner was killed when a support beam failed and dropped bags of cement mix onto him, according to the federal Mine Safety and Health Administration. Federal investigators blamed poor welding and construction.

Another miner died there in 2001 when part of the mine’s roof collapsed, and an electrician was accidentally electrocuted while repairing a shuttle car in 2003.

The mine produced 1.2 million tons of coal in 2009, according to the Mine Safety and Health Administration.

Massey Energy is a publicly traded company based in Richmond, Va., that has 2.2 billion tons of coal reserves in southern West Virginia, eastern Kentucky, southwest Virginia and Tennessee, according to the company’s Web site.

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(Drogin reported from Washington and Santa Cruz from Los Angeles.)