A coal miner was fatally injured in an Alpha Natural Resources Inc mine in West Virginia over the weekend, the company said on Monday.

It said the man was struck by material from the mine's side wall during the evening shift on Saturday at the Kingston #2 mine in Fayette County.

Alpha said operations at the mine have been idled while federal and state officials investigate.

Alpha stock was down 3.2 percent to $15.90 in morning trading on the New York Stock Exchange, but analysts noted that coal company shares generally were down on Monday because natural gas prices were hovering above a 10-year low.

Utilities are more likely to switch away from coal to fuel power stations when natural gas prices are low, they said.

Last year, Alpha acquired Massey Energy, which had operated the Upper Big Branch mine in West Virginia, at which 29 miners died in an explosion in 2010 -- the worst U.S. mine disaster in four decades.

According to the federal Mine Safety and Health Administration (MSHA) the weekend death was only the second fatality in a U.S. coal mine this year.

MSHA said its preliminary data for 2011 show that 37 miners died in work-related accidents last year -- 21 in coal mines and 16 at metal/nonmetal mining facilities. That total compared with 48 coal mining deaths and 23 at metal mines in 2010.

The agency said 2011 had the second-lowest number of mining deaths since statistics were first recorded in 1910.

According to Alpha's web site, the Kingston complex, comprising two underground mines near Pax, West Virginia, has an annual output of about 1 million tons of premium metallurgical coal for steel-making.

Last month, Alpha said it expects to produce 107 million to 124 million tons of coal this year.