From the outside, they are not the dark satanic mills of Blake's dystopia. Almost uniformly, they are painted white and carry names such as Best, Casual and Classic.
Signposts proclaim their adherence to labour laws and their intolerance of children working. But behind their towering walls, the situation is very different.
India's textile industry, worth an estimated $115 billion to the Indian economy last year and supplying the material for clothes to scores of brands for sale across India, and in Europe, America and Australia, is secretly reliant on a massive, hidden underclass of forced child labour.
Another fire at a textile factory, this time in Bangladesh, has brought renewed attention to the garment industry in the subcontinent. But much of the industry remains hidden, and in India girls as young as 11 are sold into bonded labour, compelled to work for three years on the promise of a lump-sum payment of about 50,000 rupees ($850), ostensibly for an (illegal) marriage dowry that is rarely paid.
In spinning mills, dyeing plants and garment factories, girls are kept locked in hostels, behind high walls and barbed wire, for their term of service: they are paid poorly and, hidden and young, are vulnerable to physical and psychological abuse.
The system is known as a Sumangali scheme - Sumangali is Tamil for "happily married woman" - and is pitched to poor families as a chance for girls to work in a safe environment, and earn enough money to get married.
Child-rights campaigners estimate there might be 200,000 girls enslaved in such work schemes. India's government knows about it, but efforts to eradicate it have foundered on a lack of political will and the economic might of a powerful industry.
In the village of Pirmalkoovilpatti, in Tamil Nadu's Theni district, Rajeshwari and her grandmother Padma are planning to rescue her sister Vimla from a cotton-spinning mill in Dindagal, more than two hours away.
"Soon I will go to take her back," Padma says. "They must release her, she is my granddaughter. She wanted to go there, but now she is feeling very unwell from the work, the hours are too long, the pay is low and the living conditions are very bad." Rajeshwari knows. She spent 18 months behind the walls of the same mill herself.
At 14, her contract - though she never signed a document - was for three years, at the end of which she was promised 40,000 rupees.
While she worked she earned 1500 rupees ($25) a month. This was reduced, if she missed even a single day of work, to 900 rupees.
The spinning mill was hot and noisy. She was forced into unpaid overtime and abused when production was lean.
"There were three shifts each day, so sometimes we had to work compulsory overnight shifts. I was very tired all the time and many times I had no food at all." After a year and a half, she could stand no more. Despite completing half her service, she was paid none of the promised lump sum.
While she has given up on the money, she wants her sister back. But the family's situation is complicated by the fact the broker who took a commission is a relative.
Padma was given a slice of his commission - 500 rupees, less than $10 - for allowing her granddaughter to go. Her family is poor and low-caste and they needed the money.
But it is not only poverty that drives families to sell their girls. In ultra-conservative Hindu Tamil heartland, girls are kept out of society from when they start puberty until they are married: three years physically locked away, safe from harm in their parents' eyes, and earning to pay for the marriage dowry that will be demanded of them, serves a valuable societal purpose.
A few doors away, Chhatriya Va is just home from her three-year commitment to the same mill. It took her five years to complete because she was regularly unwell (it is common practice for girls to have to work an extra month for every day of sick leave).
"I was always sick, but I had to fulfil my obligation," she tells Fairfax.
She says the cotton fibres stirred up by the spinning process made her ill and gave her breathing difficulties. "I was not given a mask. When the auditor came, we were given a mask, then it was taken away."
Chhatriya says there are about 200 girls still bonded to work in the mill. "There are young girls, 12 or 13, still working. When the auditor comes, the small girls are locked up in a room on the third floor and told to keep quiet." Neighbour Vandamani says her daughter Kavita tried to kill herself while she was bonded to work in a mill. Kavita survived, and has since left the mill.
"She was 16 then, she drank Dettol when she was not allowed to see me."
In the neighbouring village of Sathakorapatti, one of three girls Fairfax is speaking with proffers her hand, with a finger missing. It was caught in a machine at the same mill, she says.
"I received treatment, but no compensation. And then I couldn't work any more. I had to leave," she says, declining to give her name.
A man arrives outside the home, bringing all conversation, and our meeting, to an abrupt halt. We leave, and are told later that the man is a broker for mills in the area, recruiting girls to work.
Schemes to compel under-age girls into bonded labour violate numerous Indian laws, but Tamil Nadu's 5000-odd mills, dyeing plants and garment factories are economically and politically powerful.
Many mills are owned by politicians or their families, and the millions of dollars the industry brings into Tamil Nadu is vital to the state's economy and millions of families' subsistence.
About 80 per cent of girls working in Sumangali schemes in Tamil Nadu work in spinning mills. These spin the material that is then made into clothes for Indian and international markets. The massive industry is complex and supply chains are kept deliberately secret, so for global brands and Western consumers, tracing the provenance of clothes is almost impossible.
The Indian government's National Human Rights Commission has ordered the Tamil Nadu government to ensure that Sumangali and similar schemes are ended. The state's Supreme Court has heard petitions on the issue and ordered a minimum wage of 110 rupees a day, but the arcane industry is kept secret behind the high walls of the mills.
The industry's peak body, the Tirupur Exporters Association, did not return calls from Fairfax but has said previously "there is no Sumangali scheme in the Tirupur garmenting industry".
A.Aloysius from Save, a Tirupur NGO working to protect vulnerable children, says the schemes to recruit girls dissemble under ever-changing names. But regardless of nomenclature, he believes there are 200,000 girls in bonded labour across the state.
"It is not always called Sumangali, but the exploitation is the same, and it is still happening. Whatever it is called, it is forced labour, and it is illegal," Carolyn Kitto of Stop the Traffik says. The schemes are "a modern-day form of slavery".
She says that for Western consumers, the complexity of the garment industry means it is difficult to know the true provenance of an article of clothing. But she says boycotts of developing countries such as India and Bangladesh, with millions of poor families and entire economies dependent on manufacturing, are counterproductive. "Tamil Nadu needs all of these factories to stay open."
Instead, she says, consumers and Western brands need to ensure clothes are ethically sourced and made. "At the moment you can't make a perfect choice, but you can make a better choice," she says. "That's the difficulty with a garment, there are so many people who have touched it along the supply chain that could have been abused and exploited in the process.
"The fashion industry, for some people, makes a lot of money. We're asking those people to make changes that will make life better for some of the poorest or the poor."