China's major photo agency Visual China Group (VCG) pulled its website offline on Friday after the company came under fire on social media over its alleged abuse of copyright.

The row started when VCG users found the first available picture of a black hole included in the company's photo library. The company claimed copyright on the image, which means users have to pay the company if they want to use it. On its website, the company said it got the image from the European Southern Observatory, the owner of the image.

The image of a black hole on the VCG website. The company claimed copyright over the image. [Photo acquired from Weibo]

But according to a statement released on the observatory's website, their images can be used free of charge provided they are clearly credited. The observatory said it never received a request from VCG for copyright of the black hole image, and that it was illegal for VCG to claim ownership and sell the image.

The company soon came under attack from several other directions. The Communist Youth League of China took to Weibo to question VCG's right to claim copyright over China's flag and emblem. And companies including Xiaomi and Phoenix New Media announced that their logos or company photos were watermarked by VCG without their permission.

VCG apologized on Thursday for selling images of the national flag and national emblem, saying that the images were provided by contractors and had been removed from its website.

Late Thursday night, the director of VCG was summoned by Internet regulators in Tianjin and told to amend its website. The company announced early on Friday that its website would be suspended until the amendments had been made.

The company's share price has plummeted since the controversy erupted. Its shares, which are traded on the Shenzhen market, have fallen by the maximum daily limit.