TORONTO—Potash miners at the K2 mine near Esterhazy, Saskatchewan, return to the surface after being trapped underground by fire, smoke, and toxic gases for more than 30 hours. After the fire broke out, 72 miners, members of the Communication, Energy and Paperworkers Union of Canada, barricaded themselves in six underground rescue rooms January 29 that had a 36-hour supply of oxygen along with food and water.

The K2 mine (inset) is the biggest potash mine in the world, with more than 3,000 miles of tunnels running through an area stretching 12 by 18 miles. Potash is used mostly in the production of agricultural fertilizers. Taking advantage of high world prices, U.S.-based Mosaic Co. increased production in its four Saskatchewan potash mines by 21 percent in 2004.

—MICHEL DUGRÉ