According to Business Insider, Wal-Mart Stores, Inc. (NYSE:WMT) China is facing a storm of criticism for allegedly firing four workers who accused the company of food safety violations last month.

Wal-Mart China Facing Allegations Of Firing Whistleblowers

The controversy has become so incendiary that state-controlled media is joining the voices of criticism. “Relevant authorities need to step in quickly, and not let such suspected acts of revenge be carried out with impunity,” Xinhua reporter Zhang Chen wrote on Xinhua News Agency’s blog.

Statement from Wal-Mart China

When queried about the alleged retaliatory firings, Wal-Mart Stores, Inc. (NYSE:WMT) China spokeswoman Vivian Jiang told Bloomberg that the employees were terminated for “performance issues and for deviation from company policy.” Jiang continued o explicitly say, “They were not terminated for talking to the media.”

Workers made video showing unsanitary food preparation

The Wal-mart China employees who were fired accused the company of unsanitary cooking and working conditions in a video made public last month. The intense video showed worms crawling on rice and frying oil so old that it was “black as soy sauce.”

Moreover, the narrator in the video specifically claimed that Wal-Mart employees use the old, black oil to fry meat that it sold to customers, according to media sources.

Wal-Mart Stores, Inc. (NYSE:WMT) China launched an investigation after the video became public, but said it found no evidence of any food safety violations. Chinese authorities also looked into the matter and did not find any significant violations.

Food safety issues in China

However, there have been growing concerns surrounding food safety in China recently. A investigation into a large Chinese meat supplier earlier this year found the firm had been selling expired meat to a number of U.S. companies including McDonald’s Corporation (NYSE:MCD) and Yum! Brands, Inc. (NYSE:YUM).

A separate investigation earlier this year found that much of the purported donkey meat sold at Wal-Mart Stores, Inc. (NYSE:WMT) stores in China was at least some percent fox meat. The meat, which came from a local Chinese supplier, was recalled.