The Upper Big Branch Mine disaster occurred on April 5, 2010 about 1,000 feet (300 m) underground at Massey Energy's Upper Big Branch coal mine at Montcoal in Raleigh County, West Virginia. Twenty-nine out of thirty-one miners at the site were killed. The explosion occurred at 3:27 pm. The accident was the worst in the United States since 1970, when 38 miners were killed at Finley Coal Company's No. 15 and 16 mines in Hyden, Kentucky.
Wiki covers this in some detail.
[url]http://en.wikipedia.org/wiki/Upper_Big_Branch_Mine_disaster[/url]