Gun owners in the US are using Facebook's online marketplace to sell second-hand assault rifles and other weapons, using a loophole in the site's rules.
Facebook Marketplace's commerce policy specifically prohibits the buying, selling or use of "weapons, ammunition or explosives".
However, people are getting around this by disguising firearm listings as expensive gun cases or boxes, the Wall Street Journal reports.
When a potential buyer expresses an interest, they are instructed to contact the seller privately through Facebook Messenger, where details of the gun are revealed.
For example, WSJ reporters found a North Carolina listing for a gun case which would normally sell for $30 (£25) in shops, priced at $950 (£780).
When they messaged the seller, he revealed that he was actually selling an AR-15, the popular semiautomatic rifle that has been used in multiple mass shootings in recent years.
The seller shared a picture of the weapon with more than 670 rounds of ammunition, and told reporters that he had received more than 30 responses to his post within two hours.
A quick search on Facebook Marketplace by Mirror Online uncovered similar examples.
One on sale for $8,000 in Wellford, South Carolina comes with the caption: "Again for the stupid people CASE ONLY. THIS DOES NOT GO AGAINST POLICIES."
Another seller in Marion, Virginia, says: "Picture is for attention it's what's inside the case."
Anyone buying a gun on Facebook Marketplace would likely to circumvent a background check for firearms, which is mandatory in 12 US states.
Facebook Marketplace, which was launched in 2016 , allows users of the social network to buy and sell secondhand items.
It is policed by both algorithms and human moderators, to prevent the sale of illegal items.
However, it has frequently been criticised for facilitating the sale of illegal and unethical items, including drugs, weapons, animals and adult services.
Responding to the latest listings, a Facebook spokesperson said: "Selling guns on Facebook is a clear violation of our policies."
They added that any items for sale that break Facebook's rules would be immediately removed.
