British American Tobacco (BAT), the world's second-biggest cigarette company, vowed on Thursday to investigate some of its supply farms in Bangladesh after a Swedish campaign group uncovered the use of child workers to grow and process tobacco.

Swedwatch, which surveyed three tobacco farming districts in Bangladesh, said it found child labor was "widespread" in farms supplying BAT and its local subsidiary British American Tobacco Bangladesh, jeopardizing their health and education.

"Girls and boys of all ages are responsible for irrigating and leveling the field. Some of them carry loads as well and bring seedlings from the bed to the field," said the study, which was conducted between July 2015 and May 2016.

"After harvesting, they break the leaves, cut the stems, and help to monitor the kiln temperature while curing."

Swedwatch said children were not only pulled out of school to work for up to 16 hours a day during the harvest season, but were also engaged in tasks that exposed them to green tobacco plants, dust from tobacco and smoke from kiln drying.

Simon Cleverly, group dead of Corporate Affairs at British American Tobacco, told the Thomson Reuters Foundation that the company had investigated the report's findings, including allegations of unfair contracts to farmers, but found no evidence of any human rights violations.

He said BAT's investigations were consistent with the findings of several independent studies commissioned by BAT to look into tobacco growing and rural livelihoods in Bangladesh that found the company has a positive socio     economic impact.

But Cleverly said BAT, the maker of Lucky Strike and Dunhill cigarettes, has asked Swedwatch for details of the farm locations where children were said to be working so the company can investigate further and act if necessary.

"We believe this report presents a misleading and inaccurate view of our tobacco leaf farming supply chain in Bangladesh, a country where we have a long-standing history of working with farmers and the government for mutual benefit," said Cleverly.

According to the International Labour Organization (ILO), over 5 million children aged between 5 and 17 years are engaged in some kind of employment in Bangladesh.

Although Bangladesh laws set a minimum working age of 14, poverty causes many families to send children to work. But UNICEF estimates 93 percent of child laborers work in the informal sector, saying this makes enforcement of labor laws virtually impossible.

Almost half of working children are believed employed in the farm sector, which is considered the most dangerous in terms of work-related fatalities and occupational diseases due to sharp tools, dangerous machinery, and use of agro-chemicals.