More than 560 people, including women and children, have been rescued from slavery in India in International Justice Mission's (IJM) largest ever rescue operation.

Police, government officials and IJM staff released hundreds of families from forced labour at a brick kiln on the outskirts of Tiruvallur, Chennai, on Wednesday.

They instigated the operation following a call from a labourer who had managed to escape. According to a statement from IJM, he shared "stories of shocking abuse". When officers arrived, they found hundreds of people in forced labour. Families received just 400 rupees (less than £5) per week in return for working long days, from 3am every morning, and living in tents, or makeshift rooms with tin roofs.

IJM said nearly 200 children were living in the facility, almost half of whom were under five. Once they reached 12 year old, the majority of them worked alongside their parents. Pregnant women weren't given any respite, and one woman said she was forced to give birth in the kiln as she wasn't allowed to go to hospital.

"When officials explained that rescue had arrived, many couldn't believe it was real," IJM said of Wednesday's operation.

"One government officer asked the crowd 'Who wants to go free?' but he was met with a stunned silence. Slowly, one man raised his hand, then another. Soon dozens of tired hands shot into the air, ready to finally exit into safety."

There are thousands of brick kilns in India, which often employ families working as bonded labourers in order to pay off debts at huge rates of interest, effectively a form of economic enslavement.

One couple rescued on Wednesday told the Times of India that they had been brought to work at the kiln by a man who promised to loan them 17,000 rupees in return for a year's work. Struggling to provide for their two-year-old daughter after a failed harvest, the couple agreed, along with around 50 other people from their village. But upon arriving in Tiruvallur, they discovered they would not be allowed to leave the facility, and though their own daughter remained in their home town, they said the owner would physically abuse the children of other families.

"We just want to see our daughter again," they told the Times following their rescue.

IJM rescued more than 500 people from the same factory in 2011, and the owner and five others have now been arrested, facing charges under India's anti-trafficking laws and Bonded Labour Act.

"The operation highlights a critical need in the fight against slavery: If criminals remain free, the violence will continue," IJM said. "But if laws are enforced and traffickers go to jail, we can end slavery for good."

IJM is the world's largest international anti-slavery organisation, working to combat modern day slavery, human trafficking, and other forms of violence against the poor in the developing world.