The Wyoming Department of Environmental Quality is testing private wells in Hoback this week to find if benzene detected in Hoback Market's well is found in others nearby.
Benzene in Hoback Market's tap water measured 60 times the maximum allowed when the department tested it in March, and the agency says it came from the market's well. They said they are still looking for the source of the latest contamination.
Benzene is a compound found in gasoline and other sources that can cause cancer.
The environmental group American Rivers has included two Wyoming waterways in its list of the top 10 endangered rivers in the U.S. The group chooses rivers that it believes would be significantly harmed by proposed development or other activities.
The two waterways in the state are the Green River in southeastern Wyoming and the Hoback River near Jackson.