(CNN) - A flaring furnace blasts another wave of searing heat on the faces of workers hauling bricks under a southern Indian sun.

They work up to 22 hours a day propping heavy stacks of bricks on their heads. None expects to be paid for this labor. None knows how long they'll be kept here. Some are as young as three years old.

Manoj Singh was one of 149 people rescued this year from a brick kiln outside Hyderabad, India. Like millions of other Indians, the toddler was born into extreme poverty.

When CNN correspondent Mallika Kapur visited Manoj's family, now back home, he and the some of the 34 other children freed, showed her how they would make the bricks from wet clay.

"They recall from their muscle memory," says Anu George Canjanathoppil, of International Justice Mission, a non-profit dedicated to eradicating slavery around the world. "So if you ask them to explain what they did, they cannot say."

Older laborers, however, had plenty to say.

Pregnant woman kicked

According to reports from IJM investigators at the scene, one pregnant woman claimed she was kicked by her manager, when she pleaded for rest. A man had raw wounds so deep that the bone showed through.

The workers' grueling schedule permitted little time for eating. After being freed and having a full meal, many of the malnourished workers vomited.

"We had to work 18 to 22 hours a day," Manoj's father, Lucky Singh, told Kapur. "We didn't get time to eat or to bathe. One day, I dozed off. Then the boss came and beat me with a stick."

Lucky says he ended up at the kiln because he was desperate to provide for his impoverished family.

When a recruiter came to his small village in Odisha state in eastern India, near the Bay of Bengal, he willingly went on the promise of a $400 advance, which became a $400 debt - and they were locked into working to try to pay it off. They couldn't leave without permission and wouldn't be told when, or if, they could ever pay off their debt.

Bonded labor in India is the most prevalent form of slavery in the world today. It was declared illegal in India in 1976 but persists. A vast majority of India's workers scrape together a meager living through informal, unregulated work contracts, making them more susceptible to unsafe working environments and exploitation.

Illegal yet widespread problem

The CNN Freedom Project has worked for more than two years, taking aim at this illegal yet widespread practice and questioning the Indian government about its efforts to crack down on these human rights violations.

Eighteen months ago, Kapur was in the same state, reporting on the rescue of more than 500 victims from another brick kiln.

Months before, correspondent Sara Sidner filmed a three-part series showing the process for bringing entire villages out of slavery. When she asked the supervisor of a brick kiln factory to explain his use of bonded labor and why none of the workers was receiving a wage, he asked her to pay him for his answer.

At its core, slavery today exists for two reasons: greed and desperation. It's greed on the part of landowners and illegal recruiters. And its desperation for the tens of millions of people who are willing to take a risk to improve their lives, no matter how long the odds.

"Although we can't solve all the challenges of poverty or poverty itself, we can change the mindset," says Saju Mathew, the director of operations for International Justice Mission in South Asia.

"We can equip these people to know the law and their rights and to be able to identify when traps like this are laid for them. 90 to 95% of the people we have rescued are not returning back into bondage. They learn to make a livelihood in freedom."

Newly freed laborers

Working alongside the Indian government, International Justice Mission has carried out dozens of raids in the past six years. More than 3,200 people have been freed as a result.

Newly emancipated laborers are returned to their home villages, where they receive two years of community-based training and education, where they learn their rights and make plans for building sustainable businesses.

In addition, the government also provides them with 20,000 rupees, ($400) in restitution money, so they may begin to create a new life, far from the grip of illegal agents.

"For me, these are encouraging signs the government is taking proactive measures to address a very big problem. That's a shift," says Mathew. "There's been such a culture of denial, but now there is a real movement among the government officials to take on something big and confront it."

And that is all the millions of Indians like Manoj and his father would ask for.