The alleged leaking or selling of inside information about Amazon third-party merchants by Amazon’s own employees is now said to have led the giant online retailer to take action against staff members.

The moves, according to a new report in The Wall Street Journal, include firing several employees in the U.S. and India for allegedly sharing internal data that was misused by outside merchants.

In September, it was reported that brokers in China were offering to be intermediaries to buy confidential information for sellers on Amazon. That information was designed to give some independent merchants an advantage over others on the site.

Now, The Journal says, sources tell it Amazon has taken the employee action, along with deleting thousands of suspect reviews, restricting seller access to customer data, and suppressing some techniques said to game search results so that they favor one merchant over another.

“If bad actors abuse our systems, we take swift action, including terminating their selling accounts, deleting reviews, withholding funds, taking legal action and working with law enforcement,” an Amazon spokesperson told The Journal.

Amazon has been offering third-party sellers a place on its site since 2000. The growth has been dramatic, with founder and CEO Jeff Bezos writing in an annual letter to shareholders that, “In 2017, for the first time in our history, more than half of the units sold on Amazon worldwide were from our third-party sellers, including small and medium-sized businesses (SMBs).”

But along with that growth has come ever more sophisticated and complicated efforts for some sellers to gain advantage over others, notably in reviews and rankings. It has won arbitration rulings against several marketers, book authors and publishers who it accused of abusing the Kindle Direct Publishing program with a variety of tactics. It also has filed numerous lawsuits against people who allegedly offer to write fake product reviews.