Navajo Nation president Russell Begaye’s finger came up brown and oily after he ran it inside the spigot of a water tank, one of nine delivered by an EPA contractor to Shiprock, New Mexico, in the aftermath of the accident that sent orange mining waste down the Animas and San Juan rivers.

“This is what they expect our animals to drink and to use this and pollute our farmland, our canals?” said Mr. Begaye in video posted Wednesday on his Facebook page.

“This is totally unacceptable. How can anybody give water from a tank like this that was clearly an oil tank and expect us to drink it, our animals to drink it? And to contaminate our soil with this?” said Mr. Begaye. “It’s just wrong. Clearly, it’s wrong.”

In separate statements Thursday, the EPA and its contractor, Triple S Trucking in Aztec, New Mexico, told KOB-TV in Albuquerque that they will investigate the problem.

“Triple S Trucking has received assurances that each of the tanks that were used were steam cleaned and inspected prior to use at Shiprock,” said the company’s statement. “Triple S Trucking will continue to work cooperatively to investigate this complaint about contamination of the agricultural water.”

The episode comes as another black eye for the EPA, which is already under investigation for accidentally triggering the 3-million-gallon torrent of wastewater from the Gold King Mine near Silverton, Colorado, and then waiting 24 hours before reporting it.

“Every new development of the EPA spill story is worse than the last,” said Jonathan Lockwood, head of the free-market group Advancing Colorado.

In another video, Mr. Begaye draws a cup of water from the tanker’s spigot that comes up speckled with oily debris.

“It just angers us,” he said. “We told them to haul all this stuff off.”