Wal-Mart has warned two of its Chinese suppliers that purchasing contracts could be canceled in response to alleged labor violations in factories, the Wall Street Journal reported. Hong Kong-listed Mainland Headwear Holdings and Shenzhen-based Yue Wing Cheong were two of four companies mentioned in a report published in June by Playfair, an international alliance of trade unions and nongovernmental organizations. The Playfair report said that manufacturers of official Olympic merchandise were underpaying and overworking employees as well as using child labor. It prompted the Beijing Olympic Organizing Committee to launch an investigation, the results of which are due to be released in coming days. A Wal-Mart spokesman said that an audit of Yue Wing Cheong had delivered evidence of overworking but no "hard evidence" of underpayment.