By Rina Chandran

MUMBAI (Thomson Reuters Foundation) - When Chandrasekhar Reddy traveled to northeastern India in 2011, the director was looking for material for a film on forests in the region famed for its misty hills and waterfalls.

Instead, he found children as young as five working in coal mines.

Horrified yet fascinated, Reddy stayed in Meghalaya state for several months, befriending the children and their families, and slowly gaining access to the mines, many of which are illegal.

Reddy eventually gathered enough material for his first feature-length documentary, 'Fireflies in the Abyss', which was released in India last week after winning the award for Best Film in the Mumbai International Film Festival in February.

Set in the Jaintia Hills, the documentary shows young boys descending steep chutes - little more than "rat holes" - with makeshift ladders to dig coal from hard rock with just a pick axe and a flashlight.

"The fact that children were working in the mines came as a complete shock to me," Reddy told the Thomson Reuters Foundation.

"So many of my preconceived notions of what is right and wrong, the state, the law, the police, families and relationships - they were all turned on their head, as it is a very different world there," he said.

The film tells the story of Suraj, an 11-year-old boy, who was born in India of Nepali parents.

He lives with his sister and father, a miner who is drunk most of the time. His mother is dead.

Suraj desperately wants to go to school, but is expected to work to help feed the family.

Despite a law that bans child labor, India has 5.7 million child workers aged between five and 17, according to the International Labor Organization which estimates there are 168 million child workers globally.

Activists estimate that about a fifth of all mine workers in India are children. Many work for more than 10 hours a day in filthy conditions, exposed to coal dust, silica dust, noxious fumes and the risk of injury or death from collapsing mines.

"Fear won't get any work done; you need to give up worrying for your life," one of the young boys with Suraj says.

"But if you die here, it's a dog's death."

In Meghalaya, which means "abode of clouds" in Sanskrit, many workers are from the neighboring countries of Nepal and Bangladesh. They are often trafficked with the promise of good jobs, or are in debt bondage to powerful mine owners.

In a 2012 report, the National Commission for Protection of Child Rights, an umbrella group of charities, said children working in the mines in Jaintia Hills faced "hazardous conditions" with no safety or social welfare measures.

While state officials have downplayed the prevalence of child labor, the report said the presence of rat holes indicated child workers since it was "humanly not possible for an adult to enter those holes to extract coal".

In the end, Suraj gets his chance at receiving an education - with the help of some friends, who also worked in the mines.

"The mine workers live in such uncertainty, such desperation, yet there is so much camaraderie and solidarity," said Reddy.

"Perhaps that's what keeps them going, and gives some of them the hope that things can change," he said.

(Reporting by Rina Chandran, Editing by Katie Nguyen. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, corruption and climate change. Visit news.trust.org to see more stories.)