A remote tribe is reeling from widespread illness and cancer. What role did the US government play?

Remote Duck Valley reservation that straddles Nevada and Idaho has battled toxic contaminants on its land for decades .

Until recently, a now-razed U.S. maintenance building where fuel and herbicides were stored was thought to be the main culprit.

Discovery of a decades-old document with a passing mention of Agent Orange chemicals suggests the government may have been more involved in contaminating the land.

The EPA ordered the BIA to stop discharging gasoline, batteries and other fluids onto the dirt floor of the maintenance building in 1995 .

The disposal practice had long-lasting effects and the building has since been demolished with its surroundings fenced off.

The BIA says it has studied the soil and groundwater on the reservation since 1999 .

Shoshone and Paiute tribes once occupied an expanse of Nevada , Idaho and Oregon before the federal government forced them onto a reservation just under the size of New York City .

Tribal health clinic has logged more than 500 illnesses since 1992 that could be cancer.

Experts say it's nearly impossible to say with certainty that the environment factored into cancer diagnoses and deaths.