The Canadian Auto Workers (CAW) union has requested that the federal and provincial governments investigate Xstrata Plc's rationale behind the planned May 1 closure of the Kidd metallurgical site in Timmins, Ontario.

The general environment for commodities is improving, so closing the copper and zinc plant, which Xstrata acquired from Falconbridge Ltd. in 2006, is "wholly unnecessary," a CAW official said.

In December, Xstrata said it would write down the value of its Kidd...