By Frank Jack Daniel

CANANEA, Mexico, Aug 17 (Reuters) - Deep drifts of powdery rock dust blocking exit routes, exposed wiring and missing machine covers and fire extinguishers are some of the sights that greet visitors to Mexico's largest copper mine.

Miners at the Cananea copper pit, who laid down their tools three weeks ago in a strike partly over safety conditions, accuse mine owner Grupo Mexico <GMEXCOB.MX> of not investing in maintenance despite sky-high copper prices.

"They are only interested in investments to extract more minerals, not in improving safety," local union leader Sergio Tolano said.

Daniel Chavez, Grupo Mexico's director of copper operations accepted there were some problems but blamed the union for the run-down conditions in parts of the mine.

"We have hired third party companies to do this work, but they have not been able to do it because (the union) won't let them in," Chavez told Reuters. He said strikers had also sabotaged the site to make it look worse.

Grupo Mexico, which made a $1.5 billion profit last year on high prices, bouncing back from a loss in 2003, is already a major copper miner and plans to double its output after 2012.

Copper was first dug from Cananea in the 19th century and it is considered one of the world's largest reserves. The mine is the cradle of the Mexican labor movement, and one of the country's first strikes happened here a century ago.

The large sheds that house Cananea's concentrator, a system that grinds rocks to dust to extract copper, sit at the heart of the historic mine. Much of the machinery inside, not running this week because of the strike, was surrounded by massive drifts of talc-like dust that obstructed exits.

Chavez said the union had obstructed attempts to clean up the dust.

In many places rain water had turned the powder into mud that almost completely covered stairways and made the ground perilously slippery close to deep drops with no safety rails.

Emergency switches were broken and sections of ducts attached to industrial air extraction systems were missing. Machine covers were lying on the floor, leaving moving parts exposed.

Replacing machine covers was the responsibility of workers who removed them to do maintenance, Chavez said.

Discarded timber and oil barrels lay beside Cananea's ball mills, used to crush rocks, and twisted pipes hung off the walls. A fire hydrant was almost buried under a slick of mud.

Grupo Mexico said on Friday it would begin safety and pay talks with the union on Monday aimed at ending the conflict.

The company and the government say workers are using the strike to press their demand that criminal charges be dropped against union boss Napoleon Gomez, who lives in Canada to avoid arrest.

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