Swathes of Brazil's Amazon rainforest are being illegally bought and sold on Facebook's Marketplace commerce site, raising questions about the company's content moderation systems and its ethics.

A BBC investigation discovered listings on Facebook Marketplace for large plots of land in the Amazon, some covering thousands of hectares, including areas within ecological conservation zones and protected public lands and Indigenous territories.

Some of these lands were being offered at prices well below market value, potrentially indicating land-grabbing. Some sellers even offered to illegally clear the forest for potential buyers.

Many sellers openly admitted they did not have a land title, which is the only document that proves ownership of land under Brazilian law. The illegal activity is thought to have been primarily fueled by Brazil’s cattle ranching industry.

The issue raised concerns among environmentalists and indigenous communities, who claimed Brazil's government was unwilling to halt the sales and that Facebook appeared unwilling or unable to stop the listings.

The revelations provoked an inquiry by Brazil’s Supreme Court. Meantime, Facebook said it would allow the sales to continue.