Ivory Coast's cocoa industry is facing fresh scrutiny over child labor - from one of its most important export partners, the United States.

U.S. customs authorities have asked cocoa traders to report where and when they encounter child labor in their supply chains in the world's top cocoa producer, three industry sources told Reuters.

That follows increased pressure in the United States after two senators last July asked the U.S. Customs and Border Patrol, or CBP, to block the import of Ivorian cocoa produced with forced labor.

The U.S. bought around $600 million worth of cocoa beans and paste last year, around 15% of Ivory Coast's cocoa exports, and even a partial blockage could increase the cost of chocolate and have a crippling effect on Ivorian exports.

So it's not surprising, perhaps, that Ivorian authorities in January launched a major operation to crackdown on child labor in the south east of the country.

During the raids, authorities said they found children working in cocoa production, including a seven-year-old girl working in a yard sorting cocoa pods.

There are about 2.1 million children working in cocoa in Ivory Coast and Ghana according to a report published in 2018 by international civil society groups.

U.S. cocoa traders and chocolate companies including Mars, Hershey, and Cargill have repeatedly missed internationally agreed targets for reducing the worst forms of child labor from supply lines in West Africa.

But the World Cocoa Foundation, an industry body, says the use of forced child labor in Ivory Coast is rare and that banning cocoa imports would punish the innocent and push millions of poor farmers deeper into poverty.