Water samples taken after the spill showed lead concentrations in some places that were 3,500 times the normal levels.
In the meantime, state agencies are helping the EPA determine the environmental and health impacts of the accident.
EPA toxicologist Deborah McKean says the sludge laced with heavy metals moved so quickly after the spill that it would not have harmed animals that consumed it.
Southwestern Colorado residents still need to steer clear of the Animas River, officials say.
- Environmental authorities are scrambling to assess damage from the leak, caused when a plug blew at the Gold King Mine near Silverton.Read more