US Sues Fracking Company in Pa.

On the heels of a federal study that showed no ties to pollution from drilling there

The United States sued Exxon subsidiary XTO Energy, claiming its hydraulic fracking has polluted public drinking waters in Pennsylvania with toxic wastes.

The federal lawsuit was filed almost simultaneously with reports from ABC, CBS and The Associated Press that claimed a "landmark federal study" showed "no evidence that chemicals from the natural gas drilling process moved up to contaminate drinking water aquifers at a western Pennsylvania drilling site."

Both the "landmark" study and the federal lawsuit involve fracking in the Marcellus Shale formation.