Peru’s government declared an emergency across a broad jungle region Monday because of mercury contamination caused by wildcat gold mining.

The 60-day decree affects 11 districts in the Madre de Dios region bordering Brazil where studies carried out by Stanford University and others have found high levels of the toxic element in people, rivers and fish.

Deputy Health Minister Percy Minaya said as many as 50,000 people could be exposed to high levels of mercury. Particularly affected are members of the Harakmbut indigenous group, some of whom were found with mercury levels six times the suggested level.

The government said it would send hospital boats to help treat people living in the affected area, where authorities have been trying to stamp out illegal mining along rivers.

Thousands of small-time miners have descended on the Madre de Dios region in the last decade, removing an estimated 40,000 hectares (about 98,850 acres) of forest and changing the course of entire rivers.

President Ollanta Humala’s government has cracked down on illegal mining but the high price of the precious metal has proved a powerful incentive.

Peru is Latin America’s largest producer of gold and an estimated 15 percent of the country’s output is believed to be extracted illegally with little concern for the environment.