Most of the 320 labourers rescued hail from Odisha who were allegedly made to work for 12 hours per day on a salary of Rs 20.
According to a bonded labourer, they were promised salaries of Rs 350-Rs 400 per day for construction work taken up at Pudhukuppam in Thiruvallur district.
"But, we were working (brick kiln) here on a mere salary of Rs 20 per day for 12 hours," another bonded labourer said.
"We were kept working on for long hours. Most of us were not allowed to access basic food and toilet facilities," the labourer said.
He claimed that some labourers were working for several months. Some of the rescued children were below the age of 15, he added.
The owner of the brick kiln, who had employed the labourers, is absconding and a case has been registered, an official said.