Peru’s government declared an environmental state of emergency on Monday in a remote Amazon jungle region it says has been affected by years of contamination at the country’s most productive oil fields, which are currently operated by Argentina-based Pluspetrol.

Indigenous groups in the Pastaza River basin near the Ecuador border have been complaining for years about the pollution and the failure of successive governments to address it. Authorities say one reason the pollution was never addressed is that until now Peru lacked the requisite environmental quality standards.

In declaring the emergency, Peru’s Environment Ministry said the contamination included high levels of lead, barium and chromium as well as petroleum-related compounds. The region is inhabited mostly by the Quichua and Ashuar, who are primarily hunter-gatherers.

The fields have been operated for roughly 12 years by Pluspetrol, the country’s biggest oil and natural gas producer, and it will be obliged to clean up the contamination, said Environment Minister Manuel Pulgar-Vidal.

The government also said the field’s previous operator, Occidental Petroleum, had not adequately remediated contamination either. It began drilling there in 1971. Pluspetrol took over in 2001.

The 90-day emergency orders immediate action to reduce the risk of contamination to the local population.

It follows an $11 million fine levied against Pluspetrol in January.

“We know that there has been bad environmental behavior by the company,” Mr. Pulgar-Vidal said of Pluspetrol in a radio interview. “If indeed at some point remediation was done, it was not done adequately and that includes inadequate action by the authorities from 2003-2005.”

Pluspetrol did not immediately respond to telephone calls and email messages requesting comment.

Mr. Pulgar-Vidal did not describe the extent of the contamination or estimate what it would cost to clean up.

The president of the Quichua Federation of Pastaza, Sixto Shapiama, hailed the emergency as “a great achievement because for many years, decades, the government never wanted to see the reality.”

The area has for decades seen “constant (oil) spills,” said Mr. Shapiama from the regional capital of Iquitos, adding that “the sediment at the bottom of the river is completely contaminated.”

The Peruvian TV news magazine Panorama showed Reps. Marisol Perez Tello and Veronika Mendoza visiting crude-permeated rivers in the area as well as the deteriorating oil pipeline that pumps crude to the Pacific coast.

“The government is to blame because it has permitted this,” Perez said Monday.

It published on Monday, for the first time, environmental quality standards setting acceptable limits for contaminants in soil. Peru didn’t have an environment ministry until 2008 and the mining and energy ministry remains in charge of approving environmental impact statement for the extractive industries.

The investigative weekly “Hildebrand en sus Trece” reported in 2010 that Pluspetrol had 78 oil spills in the region from 2006—2010, and Shapiama blamed the spills for ailments including birth defects and spontaneous abortions.

A British religious activist who has worked with the affected indigenous populations, Paul McAuley, told The Associated Press in 2010 that he was astounded word of the contamination had hardly spread outside the jungle.

McAuley, a lay activist with the La Salle Christian Brothers, founded the Loreto Environmental Network in 2004 to support the indigenous groups in their struggle to end the pollution.

In 2010, Peru’s government tried to expel McAuley, alleging he was inciting unrest among the indigenous.

Alan Garcia, as president from 2006—2011, opened up the Amazon to mining and oil exploration and drilling. Current President Ollanta Humala has faced a backlash in the form of growing protests.