Mexican filmmaker Eugenio Polgovsky at the Morelia International Film Festival in Morelia, Mexico, in 2009. (Carlos Jasso/AP)

Eugenio Polgovsky, an award-winning Mexican documentary filmmaker best known for chronicling the struggles of the indigenous population, often against the backdrop of an indifferent society, died Aug. 11 in London. He was 40.

He spent the past two years on a prestigious creative arts fellowship at Trinity College, University of Cambridge, the first filmmaker ever invited to the post. The college confirmed the death but did not disclose the cause.

"Though he insisted that his films were not overtly political, they were marked by immense sensitivity to human beings at risk from their surroundings, especially children," said Adrian Poole, an English scholar and Trinity fellow. "He was particularly enthused by the college gardens and was deep into a new project on trees, photographing and filming them as a part of a 'visual poetry' series he called 'visual haikus.' "

That project, which Mr. Polgovsky's sister Mara has pledged to complete, is based on the structure of Japanese haiku poems, written, as Mr. Polgovsky put it, "to be read within a single breath."

Mr. Polgovsky's most acclaimed movies documented his peasant Mexican compatriots, notably the poverty-stricken, downtrodden indigenous population still treated as third-class citizens by the middle and wealthy classes, and not least the police. Those works, often focusing on child labor and industrial contamination of rural areas, have been shown at the world's most important movie festivals, including Cannes, Berlin, Sundance and the Venice Biennale.

The Mexican Academy of Film honored him with four Ariels, its highest award for excellence in filmmaking.

Director Eugenio Polgovsky at the Venice Film Festival in 2008. (Andrew Medichini/ASSOCIATED PRESS)

He won his first Ariel in 2004, for best first work, for his film "Trópico de Cáncer," a naturalistic documentary on the struggle for survival of peasant families in the central Mexican state of San Luis Potosí.

The film was shown at the Cannes and Sundance festivals, and as a special 2006 presentation in New York's Museum of Modern Art as part of a selection of the most innovative contemporary films in the Americas.

The 52-minute documentary, so titled because the scenes of the film take place on the latitude of the Tropic of Cancer, shows how indigenous Mexican children, even in the 21st century, go hunting with slingshots or bows and arrows to kill birds, rodents, tortoises, snakes or whatever they can find to provide food for their families in the same way they had done before the Spanish conquest. Once their families are fed, the womenfolk sell the rest of their catch from dawn to dusk from hot, dusty roadside stalls by Highway 57, a major trade route through Mexico.

After three years of filming, Mr. Polgovsky released the full-length (90-minute) documentary "Los Herederos" (released in English-language cinemas as "The Inheritors") in 2009, a harrowing but poetic look into the bleak lives of peasants, especially school-less children, in eight rural areas of Mexico.

It shows children working from dawn to dusk in agricultural fields, often in hazardous conditions, picking tomatoes, peppers or beans, for which they are paid by weight. Infants in baskets are left alone in the hot sun, or are breast-fed by mothers while the latter are picking crops.

The film also depicts children producing earthen bricks, cutting cane, gathering firewood and plowing fields with oxen, as well as carving wooden figures or weaving baskets to sell by the roadside.

The indelible impression conveyed, in which everyone — from the frailest elders to the smallest of toddlers — must work to survive, reveals how the cycle of poverty is passed on from one generation to another, while the middle, wealthy and political classes thrive. The film won Mr. Polgovsky another Ariel, for best full-length documentary.

"Filming without narration or musical flourishes," film critic Jeannette Catsoulis wrote in the New York Times, "Mr. Polgovsky creeps in so close that we can feel the threads sliding beneath a girl's tirelessly weaving fingers, smell the gray drinking water carried by a toddler from a scummy creek. Individual exertions — tying firewood onto a donkey or tramping mud for bricks — are stitched into a larger quilt of human survival: even a boy's fantastical figurines, lovingly carved and painted, are destined for some faraway gift shop."

In 2012, Mr. Polgovsky released "Mitote" (billed in English as "Mexican Ritual" but also meaning chaos or celebration in the pre-Columbian Nahuatl language), a fascinating 52-minute documentary filmed in Mexico City's sprawling Zócalo, or main square, considered the heart of Mexico going back to the Aztec days.

He filmed it on his own on a single day — June 17, 2010 — when the square was packed not just with its usual snakeskin-covered shamans, masked dancers, mariachis, fire-eaters, pickpockets and tourists, but also with soccer fans, who went wild as Mexico beat France, 2-0, in a World Cup soccer match shown on a giant screen.

To add to the chaos, members of the country's electricians union were on a hunger-strike in the square against job cuts.

The colorful action, which he took two years to edit, encapsulates and contrasts the spirit of Mexico old and new, pre- and post-conquest.

"Everything was on the boil, palpitating," Mr. Polgovsky told the Mexican film magazine CINE TOMA in 2014. "I had to portray this moment, which would never be repeated but summed up the condition of the country." The film was premiered to acclaim at the 2012 Rome International Film Festival.

His full-length (80-minute) film "Resurrección" (2016), conceived and edited while at Trinity, tells the story of one peasant family's efforts to reclaim a paradise lost, the area around the Salto (waterfall) of Juanacatlán, near the city of Guadalajara and known as "Mexico's Niagara."

The waterfall traditionally sustained many surrounding peasant villages, their fishermen and farmers, but it became polluted by encroaching industries and factories, bringing sickness and death to the villagers.

Eugenio Gregorio Polgovsky Ezcurra was born in Mexico City on June 29, 1977, to Miguel Polgovsky, son of a Russian émigré who had fled during the 1917 revolution. Eugenio's Argentina-born mother, Rosario Ezcurra, was herself an émigré, an anthropology and visual arts student who fled her country after the 1976 military coup that launched the bloody "dirty war."

Mr. Polgovsky attended primary and secondary school at Mexico's Colegio Madrid, where he won his first photography award in an international photography contest organized by United Nations Educational, Scientific and Cultural Organization (UNESCO).

In 2003, he graduated from Mexico's Centro de Capacitación Cinematográfica, a state-funded film school, with a bachelor's degree in film directing and cinematography. In 2007, he founded his own production company, Tecolote Films. (In Nahuatl, a tecolote is an owl, or more recently a cop).

Survivors include a daughter from a relationship; his mother and father; two sisters; and two half-siblings.

In June, Trinity College laid on a 40th birthday dinner for Mr. Polgovsky, starting at the college's High Table before moving on to a midnight, candlelit punt on the river Cam, to which he had invited the college's porters, gardeners and other staff, all of whom he knew by name. On the river, Mr. Polgovsky read poetry by Allen Ginsberg while his sister Mara, a junior research fellow at Queens' College, University of Cambridge, read works by Charles Baudelaire.