Mining firm Grupo Mexico has set side $147 million to pay for damages from a massive acid spill that contaminated waterways in the northwest of the country, officials said Thursday.

Two subsidiaries of the company will pay for the clean-up and compensate people who suffered material damage in the August 6 environmental catastrophe in Sonora state, which saw sulfuric acid leak out of a copper mine holding tank and into a stream that serves two rivers.

The subsidiaries "have taken on the obligation to completely fix the environmental damage and pay for the material damage" caused to 21,000 families, said Environmental Minister Juan Jose Guerra Abud.

The minister said the mining group pledged to provide more funds if needed to clean up the worst environmental disaster on record for the mining industry in Mexico.

Economy Minister Ildefonso Guajardo said the government would not close the Buenavista copper mine, one of the biggest in the world with annual production of 200,000 tonnes.

Keeping the mine open would preserve jobs, he said.

The company has also been fined $3 million.

Tests at the two affected rivers found higher-than-permitted levels of copper, arsenic, aluminum and lead and triggered a political clash between the administration of President Enrique Pena Nieto and Sonora Governor Guillermo Padres.