MEXICO CITY, Sept 1 (Reuters) - Grupo Mexico, a metals miner and railroad operator, said on Monday that operations at its Buenavista mine were not affected by a search of its offices late last week by the federal prosecutor's office, part of an investigation into a toxic spill.
Mexico's environmental prosecutor said the copper mine, one of the world's biggest, released 40,000 cubic meters of toxic mining acid into the Bacanuchi River in the northern state of Sonora last month.
"At no point did (the search) affect the functioning of the mine complex, which continues operating normally," Grupo Mexico , said in a statement, adding that the search which began on Friday concluded on Saturday.
Grupo Mexico is in the midst of a $3.4 billion expansion project at the mine, which has the largest proven copper reserves in the world. The expansion aims to boost production capacity to 1.3 million tonnes by 2017. (Reporting by Alexandra Alper and Veronica Gomez; Editing by Simon Gardner and Jeffrey Benkoe)