Mexico City, June 22 (teleSUR-RHC)-- A Canadian mining company has spilled an estimated 1,200 gallons of toxic waste into a river in the central Mexican state of Guanajuato, Mexican media reported Saturday.

The leak into the Cata River in Guanajuato City at the site of Great Panther Silver's mining operations was caused by a rupture of an eight-inch pipe transporting mining tailings, leaking the toxic mud-like mining waste into the river.

Mexico's federal environmental protection body known as Profepa is investigating the spill to assess the extent of water and soil contamination and presence of dangerous substances. Profepa has indicated that it intends to level fines against Great Panther Silver as a penalty for the contamination.

Great Panther Silver has denied the toxicity of the spill, saying in a statement that the mining tailings do not contain heavy metals, chemicals, or other dangerous substances. Toxic substances used in mining to separate precious metals from the earth, such as cyanide in gold mining, remain in tailings at the end of the extraction process. Safe handling and storage of mining tailings is considered among the most critical environmental concerns of mining operations, as a tailing pond breach or other major spill can cause catastrophic damage to rivers, soil, and groundwater. Most mining tailings are permanently stored in isolation from the surrounding environment to avoid contamination.