GILLETTE, Wyo. (AP) — Union Pacific Corp. shipped 18 percent less coal from the Powder River Basin in northeast Wyoming during the second quarter this year.

The Omaha, Neb.-based railroad shipped 36.1 million tons of coal from the basin. In the second quarter of 2011, the company shipped 44.2 million tons of coal.

UP executive attribute the decrease to market conditions and the ongoing impact of some contract losses.

Union Pacific has railroad track in the southern part of the basin and ships from coal mines to utilities.

The Associated Press reports  that coal shipments during the current third quarter appear to be improving, thanks to climbing natural gas prices.