CHARLESTON, W.Va. — Global demand for coal has shown some signs of slack, leaving investors to wonder what's next for U.S. producers who've seen prices at times triple over the past year.

Ocean freight rates, the U.S. dollar and other factors behind the big jump have begun to ease. Meanwhile, analysts are questioning whether a global slowdown has begun to hurt the steel industry, which uses high-priced metallurgical coal to fire blast furnaces.

Investment bank Goldman Sachs downgraded the entire U.S. steel industry Thursday, citing risks such as the strengthening dollar and concerns about demand from China.

Shares in one of the biggest coal producers, Massey Energy Co. tumbled nearly eight per cent, or US$4.37, to $51.40 Thursday on news that 2008 prices and production are showing signs of weakness.