CHENNAI, India (Thomson Reuters Foundation) - Police have rescued 10 teenage boys, allegedly trafficked and held in bondage in a shoe-sole factory in the southern Indian state of Karnataka, after a tip-off from a children’s helpline.

Hundreds of children, mostly from poor rural areas of northern Indian states like Bihar, are brought to Bengaluru in Karnataka every year by agents who sell them into bonded labor or hire them out to unscrupulous employers, activists say.

“I sneaked out one night and bought a telephone card,” teenager Adhir Paswan, 18, told the Thomson Reuters Foundation in a telephone interview.

“I made the distress call to our families and a helpline in Bihar. We were not being paid and the younger boys were being beaten and abused.”

One of the boys, 17, said in a statement they hadn’t been paid in over a year.

Earlier this month, six boys from Bihar were rescued from a decoration-making factory in Bengaluru.

A 2015 report by the International Labour Organization puts the number of child workers in India aged between five and 17 at 5.7 million, out of 168 million globally.

More than half of India’s child workers labor in agriculture and over a quarter are in the manufacturing sector.

The government has recently amended its child labor law to permit children to work for their families and reduce the number of banned occupations for adolescents.

“The sole factory was a miserable place,” said Lakshapathi Pendyala of the Association for Promoting Social Action, a charity that runs a helpline in Bengaluru that was part of the rescue team.

“The boys were working from nine in the morning to nine at night. They were made to sleep in the workplace only, which was filled with the smell of glue used in sticking the soles,” Pendyala told the Thomson Reuters Foundation on Friday.

“Several chemicals and glues were being used by the boys without any protection and some of the boys had deep cuts on their palms.”

In a statement, rescuers said the boys, aged between 14 and 18, had been brought to Bengaluru from Sitamarhi district in Bihar state by at least five different traffickers.

The boys had been working at the factory for between one and 14 months.

In their accounts to officials, the boys said they were forced to work throughout the day with breaks for meals only. None were allowed to call or visit their families.

Paswan said they had been promised wages of 7,000 rupees ($105) a month. Most said the money had been sent for a few months to their parents and then discontinued.

Police have registered a case against the owner of the factory and two traffickers under anti-slavery legislation.

They arrested two people. The factory owner is at large, investigating police, said in an interview, requesting anonymity.