Chinese?business news website 21cbh.com has had its license revoked and all staff have been laid off, Xinhua news agency reported on its mobile application on Friday night.

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The move came as top media regulators in Guangdong launched an investigation into the website for allegedly extorting money from companies in return for positive coverage.

Journalists suspected of serious economic crimes have been put under criminal investigation, according to the website of the Administration of Press and Publication of Guangdong Province.

Nanfang Media Group, the website's parent company with headquarters in Guangzhou said it has sent a working group to the website and newspaper, according to a Nanfang Daily reports, one of Nanfang Media Group's newspaper outlets.

The administration also requires other Guangdong publications, especially the financial media, to carry out self-inspection.

Police say the business news website and two public relations firms collaborated to extort money from companies in return for favorable coverage and withholding negative news reports on the site. If companies refused, the website would publish negative or malicious information about the company.

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The list of victims covers many listed companies and famous enterprises from Beijing, Shanghai and Guangdong that are planning to go public, restructuring or making a business transition.

Confessions by suspects show "too many companies" were 21cbn's victims, but only a few reported the matter to police.

The case involves eight people including journalists, media heads, marketing staff and public relations heads, all of whom have been detained by police, on suspicion of extortion.

They include Liu Dong, president of 21cbh.com, Zhou Bin, the website's editor-in-chief, and reporters and employees of its marketing department, as well as heads of the two PR firms. Together, they are alleged to have extorted money from more than 100 companies since November 2013, said police.

21cbh.com is run by Guangdong-based 21st Century Media Co., Ltd., which claims on its website to be "the largest professional media operator in the Chinese financial and business media industry."

The company's publications include 21st Century Business Herald, Money Week and 21st Century Business Review. 21cbh.com has offices in Shanghai, Beijing and Guangzhou.

Chinese authorities have been undertaking a crackdown on extortion in the media and paid-for news coverage.

They have discovered problems including press cards being issued to people who are not journalists, and newspaper websites being contracted to carry advertisements.