Indigenous Peruvian plaintiffs on Monday won a key round in their contamination lawsuit against Occidental Petroleum Corp. as a federal appeals court allowed the case to proceed in the United States.

The Ninth Circuit Court of Appeals overturned a lower court ruling that the case should be heard in the Peruvian courts. The plaintiffs had sought to have the case against the Los Angeles oil exploration company heard here because of concerns of corruption in the Peruvian courts.

The lawsuit was initially filed in 2007 in U.S. District Court in Los Angeles by Washington D.C.-based Earth Rights International and the Venice civil rights law firm of Schonbrun DeSimone Seplow Harris & Hoffman LLP on behalf of 25 members of the indigenous Achuar community in northern Peru.

The suit seeks to have Occidental clean up contamination and compensate all of the Achuar people for allegedly dumping 9 billion barrels of toxic oil byproducts into local rivers and streams for more than 30 years.

In 2008, a U.S. District Court judge in Los Angeles ruled that the case should be heard in the Peruvian courts, since the allegations concerned events that occurred in that country.

Occidental Petroleum’s position has been that it sold its oil field holdings in Peru to Argentinian oil company Grupo Pluspetrol in 1999, and as part of that transaction, Pluspetrol “assumed responsibility for past, present and future operating conditions” in the oil field.

Richard S. Kline, Occidental’s vice president of communications and public affairs, reiterated that position Monday, and added that the company does not believe its operations harmed the peoples.

“We have empathy for the continuing issues the Achuar people have raised with Pluspetrol and the Peruvian government, but to our knowledge there are no credible data indicating negative community health impacts resulting from Oxy’s operations,” he said, adding the company “met applicable government requirements and industry standards” when operating there.