Chinese authorities have issued arrest warrants for 19 e-commerce vendors who provided buyers of virtual reality (VR) gadgets with free pornography, state news agency Xinhua reported Thursday.

The first warrant was issued on Dec. 15 in Shenzhen, the southern Chinese tech hub across the border from Hong Kong. That suspect, identified only by his surname, Liu, ran a store for VR glasses on the upscale online shopping website Tmall, which is owned by internet giant Alibaba. To attract more customers and generate greater profits, Liu had sent pornographic videos to over 700 people, according to the report.

Since then, Shenzhen authorities have issued warrants in nine more cases, all regarding e-stores that sell VR glasses and throw in adult videos for free. The store operators delivered the freebies via chat groups, cloud services, or storage cards shipped with the VR equipment. It’s not clear whether the videos were virtual reality or regular files.

An advertisement on a Taobao shop implies that virtual reality glasses can be used for unsavory purposes.

According to an online statement by the Shenzhen People’s Procuratorate, the public prosecution office that approved the arrests, some suspects said that giving out pornographic videos had become a common practice and an “unwritten rule” in the VR sales business. The procuratorate could not provide immediate comment when contacted by Sixth Tone on Friday.

Pornography is illegal in China, where a 1997 law bans the production and dissemination of obscene content. Violators face punishments ranging from fines to jail time, depending on the severity and scope of their crimes.

In recent decades, an expanding internet has meant authorities have had to police an ever-increasing number of ways in which pornographic material is spread. As checking for illegal content has become more and more cumbersome, many Chinese internet companies have shut down their cloud services altogether. In September 2016, the CEO of QVOD, the company behind now-offline streaming application Kuaibo, was given a 42-month jail term and a fine of 1 million yuan ($144,000) for lewd videos disemminated on the platform.

Searches on e-commerce platforms Taobao and Tmall for “VR glasses” return several shops advertising with erotic images and messages implying that free porn is available for paying customers. “Unlimited materials for free,” read a banner on one e-store. At a Tmall shop that sells a Chinese brand of VR goggles, one customer’s telling review informed prospective buyers that “the storage card has quite a few resources — you know the kind I mean.”

(Header image: An employee holds a pair of virtual reality glasses at a mall in Beijing, Nov. 27, 2016. Kevin Frayer/Getty Images/VCG)