BERLIN (AP) — German authorities said Friday that they have shut down online marketplaces for illegal drugs that used the encrypted messaging service Telegram.

Prosecutors in Frankfurt said police across Germany and in neighboring Austria on Thursday took control of nine chat groups with a total of about 8,000 members.

Authorities said they have so far identified 28 people suspected of selling narcotics, forged documents, illegally obtained data and other items via Telegram.

The groups shut down had names such as “Silk Road,“ ”GermanRefundCrew“ and “Cracked Accounts Shop.”

Prosecutors said the Telegram groups were used to advertise wares, while sales were conducted in private direct chats.