BILLINGS, Mont. (AP) - A U.S. Interior Department investigation glossed over the federal government's negligence in a massive toxic wastewater spill from an inactive gold mine that fouled rivers in three states, Republicans in Congress said as they pushed for a more detailed explanation of the accident.

BILLINGS, Mont. (AP) A U.S. Interior Department investigation glossed over the federal government's negligence in a massive toxic wastewater spill from an inactive gold mine that fouled rivers in three states, Republicans in Congress said as they pushed for a more detailed explanation of the accident.

An Environmental Protection Agency cleanup crew triggered the 3-million-gallon spill on Aug. 5 during cleanup work near Silverton, Colorado. It sent a torrent of rust-colored water filled with poisonous arsenic, lead and other contaminants rushing downstream through communities in Colorado, New Mexico and Utah.

The Interior Department's subsequent investigation conducted at the EPA's request faulted EPA officials for not taking steps that could have prevented the accident.

But House Natural Resources Committee Chairman Rob Bishop told The Associated Press that the Interior investigation was too limited and failed to answer whether any criminal conduct occurred.

Interior Secretary Sally Jewell was scheduled to testify on the matter before Bishop's committee on Wednesday.

Federal officials have yet to release documents related to the investigation that The AP has sought through public records requests. That includes criticisms over the scope of the probe from a U.S. Army Corps of Engineers geotechnical engineer who peer-reviewed the agency's work.

Among the questions still unanswered is why EPA's cleanup crew was seemingly caught unaware by the accident. A June 2014 EPA work order warned of the potential for a catastrophic blowout from the Gold King Mine after pressurized water built up inside the collapsed entrance to the mine.

The spill occurred when workers for EPA and its contractor, Environmental Restoration LLC, started excavation work that was intended to allow them to safely drain the mine.

"Why were they digging with such ferocity when there were concerns expressed a year ago about what would happen?" asked Bishop, a Utah Republican. "One way or another, we're going to get to the truth."

The response to the Gold King spill has cost the EPA almost $17 million through November 24, according to an agency spokeswoman.

Jewell said Interior conducted a thorough and independent review of the accident. It found that the problems seen with Gold King were prevalent in the tens of thousands of abandoned mines that dot the Western U.S.

The administration of President Barack Obama is seeking to charge mining companies a fee to fund cleanup work at such sites, but Republicans in control of Congress have so far resisted the idea.

"Due to the abandoned nature of these sites, the public is often left with the bill for remediation," Jewell said in her prepared remarks. "It's unfortunate that the catalyst to address a problem is often an incident like this."

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