Armed with territorial knowledge, rubber boots, smartphones and drones, indigenous Amazonians in Peru are doing what state and private oil companies have long failed to do: report oil spills that have been polluting their corner of the rainforest for decades.

Fidel Sandi, 33, a leader in the indigenous Achuar community of San Cristobal, plunges a stick into the spongy soil of a palm swamp and watches as sticky crude bubbles to the surface leaving an oily sheen on the water.

“The trees are drying out, the people gather fruit here for the market, there are animals here that they hunt, but everything is polluted,” Sandi sighs with a mixture of anger and exasperation. Gazing at the palms, he has a keen eye for the signs of oil contamination. Now he can use his smartphone to gather geo-referenced photographic and video evidence to report to Peru’s environmental supervision agency OEFA .

His community still collect aguaje palm nuts and hunt peccary in this patch of wetland, part of Oil Block 8 which has been concessioned to Pluspetrol, the largest oil and gas producer in Peru, for the last 15 years. A company sign says it was environmentally remediated in 2009 but Sandi says crude deposits mean the food chain is contaminated. Oil drilling began around his village on the bank of the Corrientes river before Sandi was born.

Oil contamination is not just a problem for this Achuar village but for fellow communities upriver; in the neighbouring Pastaza river basin; for the Kichwa in the Tigre river and the Kukama and Wampis in the Marañon and Santiago rivers, across a swath of Peru’s northern Amazon.

Environmental monitors have come from all these places to San Cristobal to learn how to use this technological toolkit with a team from the International Institute of Social Studies at Holland’s Erasmus University and the NGO Digital Democracy.

“With the internet and drones we can get images from the depths of the Amazon to the boardrooms of companies in a matter of seconds when before it would take days or weeks,” says the NGO’s Gregor MacLennan.

“The modern world is already here in the shape of the oil companies. We believe that indigenous people need to be able to fight on equal ground.”

Rafael Rojas, in charge of hydrocarbons supervision at OEFA says the drones “help to determine the affected areas with much greater speed and accuracy” when there is an oil spill. There have been scores of spills in the last year particularly linked to the deteriorating North Peruvian pipeline run by the state oil operator Petroperu. Petroperu has said it will expand the pipeline’s infrastructure and has a contingency plan in place to deal with spills.

San Cristobal’s oldest residents can chart the oil drilling’s deadly legacy back more than 45 years. Sandi’s mother, Anacha Hualinga, says she doesn’t remember a time before there was oil in the Corrientes river. She believes its toxic impact has tragically marked her life.

“My son died vomiting blood. My children have died, also my grandchildren, because of the contaminants, their bodies could not endure them. Others were born dead because they could not bear the pollution,” she said. Two of her children died as infants and three of her many grandchildren also died very young, she explained.

“Today it continues, children are born with pains or wounds. For me it is very painful to lose my children and grandchildren.”

In 2006, Peru’s health ministry found more than 90% of Achuar men, women and children in the Corrientes basin had levels of toxic-heavy metals in their bloodstream well above safe norms. In the same year, Pluspetrol signed an agreement pledging to reinject production waters laced with heavy metals such as lead, cadmium and barium deep into the ground so they would no longer enter the water cycle.

Pluspetrol, which has run the nearby oil block since 2001, has blamed a previous operator – the US-based Occidental Petroleum – for the pollution. In 2015 the US company paid an undisclosed sum to the Achuar people in an out-of-court settlement.

Pluspetrol did not respond to questions.

Peru’s health ministry has yet to carry out a toxicological study in the area and the people receive no medical attention for their specific symptoms, says América Arias, a public health specialist working for Equidad, an NGO.

“Conditions are starting to emerge which can have no other cause than the pollution; cancer cases, deformities in newborn babies, congenital diseases, low cognitive development in children,” she said. Several scientific studies show the build-up of heavy metals in soils, as well as fish and animals consumed along the Corrientes, is potentially carcinogenic.

The Amazon region of Loreto is one of nine regions in Peru where toxic-heavy metals produced by mining and oil drilling are damaging health, according to Amnesty International. Representatives have petitioned the government in Lima demanding a specific health plan and potable water.

After a visit by the delegation, Peru’s health ministry said it would coordinate with the environment, housing, finance and energy and mines ministries to control and reduce the causes of the contamination.

But Peru will have to start from scratch, says Fernando Serrano, an occupational health professor at the University of Missouri and an expert on toxic-heavy metal pollution.

“To this day there is no national assessment of how many people have been exposed to lead, cadmium, arsenic, mercury … and many other toxic metals which we know cause disease,” he said.