CHARLESTON, W. Va. - The U.S. coal industry had its deadliest year in nearly two decades in 2010, with much of the death toll stemming from a single explosion.

As of Thursday, 48 miners had died in the nation's 1,500 coal mines over the last 12 months - including 29 who were killed April 5 in a blast at Massey Energy Co.'s Upper Big Branch mine. This year's was the highest death toll since 55 were killed in 1992, according to data from the federal Mine Safety and Health Administration. And it was much higher than the 18 killed in 2009, the industry's lowest tally since 1900, according to federal records.

State and federal investigators say their report on what caused the Upper Big Branch blast, the deadliest U.S. coal-mine explosion since 1970, won't be finished until late next year.

"Everyone in the industry is concerned about 2010 and what we saw there and is taking a look at all aspects of mine safety," said Carol Raulston, a spokeswoman for the National Mining Association, an industry trade group.

MSHA officials declined to address the 2010 death toll until the year is done.

Many of the 2010 deaths were caused by gas explosions, moving equipment, and other factors long thought to be under the industry's control.