One of the biggest drug marketplaces on the dark web has abruptly shut down.
The Evolution site closed as its administrators went offline reportedly taking with them bitcoins people had deposited with the underground bazaar.
The two administrators are believed to have absconded with about $12m (£8m) in bitcoins.
Evolution was one of several drug-selling sites that filled the gap created when a similar site, the Silk Road, was closed down in 2013.
The Evolution marketplace was a hidden site on the Tor network. This system is used by many people to hide their identity and location and others have found ways to host sites on it in a similar fashion to those found on the wider web. The Tor network conceals information by bouncing data through several different machines and encrypting it at every step.
According to tech news site Ars Technica the marketplace let people buy illegal drugs, stolen ID information, weapons and hacking services. Payment for these goods and services was only made using bitcoins. Evolution offered an "escrow" service which let people deposit bitcoins on the site to help speed up the sales process.
Security expert Brian Krebs said this meant the administrators had "direct access to a tempting amount of virtually untraceable currency".
The temptation appears to have been irresistible, said Mr Krebs, as many people who bought and sold via the site took to social news site Reddit to report the administrators had absconded with their escrowed bitcoins.
Evolution rose to prominence following the closure of the Silk Road site in 2013 following raids by the FBI and other US law enforcement agencies. It also prospered when the Silk Road 2.0 went offline.