Sonora, Mexico - Mexican authorities have issued a binational alert after a new toxic spill was confirmed in Sonara, Mexico - from the same copper mine that spilled 40,000 cubic meters of sulfuric acid into the Bacanuchi River in August. Authorities are testing water in southern Arizona for contamination that has made its way into the San Pedro River, which runs northward from Cananea into Pinal County.

Sonora's civil protection union said it has "implemented protocols to protect the population after confirmed reports of a toxic spill from the Buenavista del Cobre mine" - a subsidiary of Grupo Mexico.

The agency is urging some 25,000 residents of the area to avoid using the water.

During an overflight of the mine on Sunday, PROFEPA, Mexico's environmental protection agency, observed water flowing over the top of the Cananea dam. Triggered by heavy rains from Hurricane Odile, the overspill may have cause contaminated water to flow into the San Pedro River.

Arizona authorities say they are trying to get more information about the potential spillover, but Mexican officials have not said how much waste leaked, or what exactly was in the spill.

"From what I understand from the Mexican authorities, they doubt there is any higher level of contamination," Cochise County Emergency Services director Norman Sturm Jr. said on Monday. "But because that dam is near the mines in Cananea, I'm assuming they're just trying to be cautious."

Sally Spener, spokeswoman for the International Boundary and Water Commission, said it could be days before Mexican authorities sampling the water near the border get lab results back. The water will be tested to determine whether it contains heavy metals or other contaminants such as arsenic and if it made it to Arizona.

The office of the Federal Attorney General for Environmental Protection states that the spill contained "rainwater overflow with ferrous elements below the threshold of what would pose a human health risk to human health," and officials are therefore not warning the public of any contamination.

The mine's August spill contaminated water reaching seven towns, affecting a total of about 20,000 inhabitants. Grupo Mexico has set side $147 million to pay for damages and has also been fined $3 million.

On Friday, the Sonora government announced a break with the company, saying mining executives have hampered investigations and lied about the measures it has taken to control the effects. They have also called for scrapping the concession to Grupo Mexico after what is considered the worst environmental disaster in recent times for the country's mining industry.

The federal government has said that it will temporarily or permanently suspend the company's rights to use the mine.

The Buenavista copper mine is one of the biggest in the world, with annual production of 200,000 tons.