The organizing committee, known as Bocog, said the violations included the use of child labor at one factory, Le Kit Stationery Co. Bocog is terminating Le Kit's right to manufacture Olympic merchandise and revoking its licensing agreement, said Sun Weide, spokesman for the committee.

It is also suspending the right of the three other manufacturers to design Olympic products, although the companies will still be able to make the products, Mr. Sun said.

The committee's investigation appears to support the findings of a June report by the Playfair Group, an international group of trade unions and nongovernmental organizations, which first raised these issues.

The organizing committee said the three other manufacturers--Mainland Headwear Holdings Ltd., Yue Wing Cheong Light Products (Shenzhen) and Eagle Leather Products--had made employees work excessively long hours, a common problem in China's factories. Bocog said those factories will be required to improve operations in line with local labor laws immediately.

Officials at Eagle Leather and Le Kit couldn't be reached for comment. Lawrence Li, spokesman for Yue Wing Cheong, said the company could comment only after speaking to Bocog.

Mainland Headwear co-founder Pauline Ngan said the problem was due to misunderstandings over overtime standards. Mainland Headwear, with its export-oriented clientele, has maximum overtime rates of 60 hours per month, which is in excess of local labor regulations of 36 hours per month, she said. She said Mainland Headwear would comply with local regulations on overtime in the future.

At the time of the June report from Playfair, Mainland Headwear's chief executive, Peter Ho, said the report's findings were "groundless" and "outrageous."

Mainland Headwear and privately held Yue Wing Cheong are also suppliers to global retailer Wal-Mart Stores Inc. Following the Playfair report, Wal-Mart conducted its own audit of the two manufacturers and issued warnings after finding them guilty of overworking staff.

Another Mainland Headwear client, the U.S. National Basketball Association, said it conducted an unannounced audit of the company through their licensee Drew Pearson/Concept One and identified several areas that need correction, though the NBA didn't specify what these were.

To sign up for The Wall Street Journal Briefing please visit http://www.briefing.wsj.com/hktdc.