That was the scene that greeted CNN in 2011, when it visited a brick kiln in Varanasi district in India's most populous state, Uttar Pradesh. There, these workers are known as bonded laborers, bound to those who gave them or their forefathers an advance or a loan. Bonded labor is illegal in India, but enforcement is lax.
Four years later, the CNN Freedom Project
returned to a Varanasi. At a brick kiln, workers toil tirelessly in the heat; on the surface it appears much the same as on our last visit, but there is an intangible change. We meet a worker who says she's too scared to talk to us -- but she's not being forced to work and she is taking home a wage.
The workers here are getting paid -- they get a token for every 10 bricks they carry and the manager says that on an average, each worker can carry about 3,000 bricks per day, earning about 60 rupees -- equivalent to $1.
It's a very low wage but these workers are unskilled and illiterate and they are unaware of government subsidies that could help them, so they continue to be exploited. But they're not bonded laborers.
"So much has changed in the last four to five years," says activist Bhanuja Lal Saran, of Free the Slaves
. "The employers now understand they are breaking the law and will be prosecuted, the laborers are more empowered and aware of their rights, and the government is more active and accountable."
Activists say an investigation was launched just weeks after CNN's visit in 2011. A neighboring brick kiln was raided and the bonded laborers were freed.
At this kiln, the workers get time off and the children are no longer made to work. They're not in school, but the authorities say this is a good first step.
P.K. Singh, Labor Commissioner for Varanasi, acknowledges bonded labor is still very much an issue in India, especially in rural areas. With no chains and no armed guards, it's hard to detect.
But as more and more of India's workforce is lifted by the country they helped build, activists say there is hope that brick by brick, a transformation may be under way.
Watch the video
above to find out more.