CHENNAI, India (Thomson Reuters Foundation) - The rescue of two toddlers in India who were held captive at a brick kiln to ensure their mother returned to work to repay a debt exposes a widespread abuse, campaigners said on Wednesday.

Tamil Nadu state officials said they reunited the boys, aged 1 and 3, with their mother Bhavani Kumari on Tuesday and have registered a case of bonded labor with the police against the kiln owner.

“The children were forcefully taken from the mother,” a district official E Selvaraju told the Thomson Reuters Foundation.

“The supervisor at the kiln wanted to make sure that the mother returned from her village and continued to work to repay a loan of 15,000 Indian rupees ($233).”

India banned bonded labor in 1976 but it remains widespread, with millions from marginalized communities working to repay debts to employers or moneylenders.

Employers often keep children as collateral when their parents travel home for weddings or funerals, campaigners said.

“Families trapped in debt bondage are never allowed to leave together,” said Sarvanan Rajendran, a member of the Cheyyar bonded labor vigilance committee, who initiated the rescue.

“Someone is always held captive at the kilns and it is often the children. It is a way to ensure that workers come back.”

He said Kumari and her husband earned 600 rupees for every 1,000 bricks they made and had not been allowed home for two years and Kumari’s husband went missing a month ago.

In a statement to officials, Kumari said she did not earn enough to feed her family because she could not meet the quota.

She went home to look for her husband and borrow some money from her in-laws but was waylaid by two men on a motorcycle who snatched her children, it said.

Some 500,000 manual laborers in 11 industries in Tamil Nadu are trapped in debt bondage, the majority working in brick kilns, according to the International Justice Mission, an anti-slavery organization.