On Sunday, The Wall Street Journal published a report that revealed that sellers have bribed Amazon employees to get access to internal sales data or to delete negative reviews, and that the company has launched an investigation into the practice.

According to the report, middlemen use social media sites like WeChat to track down Amazon employees, offering them cash to turn over internal information or to delete negative reviews. The WSJ also reports that it costs roughly $300 to take down a bad review, with brokers “[demanding] a five-review minimum” per transaction. Amazon employees have also been asked to provide e-mail addresses of customers who left negative reviews, or to provide sales information to give sellers an edge against their competitors. To combat the behavior, an Amazon spokesperson told the WSJ that it has implemented “systems to restrict and audit what employees can access.”

The practice “is particularly pronounced” in China, although the company’s investigation extends to US employees as well. An Amazon spokesperson confirmed to The Verge that it was investigating the claims:

We have strict policies and a Code of Business Conduct & Ethics in place for our employees. We implement sophisticated systems to restrict and audit access to information. We hold our employees to a high ethical standard and anyone in violation of our Code faces discipline, including termination and potential legal and criminal penalties. In addition, we have zero tolerance for abuse of our systems and if we find bad actors who have engaged in this behavior, we will take swift action against them, including terminating their selling accounts, deleting reviews, withholding funds, and taking legal action. We are conducting a thorough investigation of these claims.

Update September 16, 5:13PM ET: Updated with Amazon’s statement to The Verge.