Kevin McCoy

USA TODAY

Retail giant Wal-Mart Stores and warehouse membership club leader Costco say they're taking action in response to a news investigation that found evidence of forced labor in their Thailand-area seafood supply chains.

Workers compelled to toil for years in Asia at no pay and under threat of violence are being used in the production of seafood sold by Wal-Mart, Costco and major British and European retailers, England-based The Guardianreported Tuesday.

Other major European-based multinationals and retailers also sell seafood linked to the forced labor, the report said.

The forced labor enslaves large numbers of men who toil in the waters off Thailand aboard fishing boats that are vital to production of shrimp sold to the major food retailers around the world, the newspaper reported.

One of the world's largest shrimp farmers, Thailand-based Charoen Pokphand (CP) Foods, buys fishmeal used to feed farmed shrimp from some suppliers that "own, operate or buy from fishing boats manned with slaves," The Guardian said it found during a six-month news investigation.

Men who escaped from boats that supply CP Foods and similar companies described 20-hour work shifts, regular beatings, torture and even murder, the newspaper reported.

Major companies that sell the seafood to consumers told The Guardian they condemned human trafficking for forced labor and conducted audits designed to detect and stop illegal practices.

According to the newspaper, Wal-Mart, the world's largest retailer, said: "We are actively engaged in this issue and playing an important role in bringing together stakeholders to help eradicate human trafficking from Thailand's seafood export sector."

Costco told the newspaper it is requiring its suppliers of Thai shrimp "to take corrective action to police their feedstock sources."

Several companies also said they have joined Project Issara (Project Freedom) a public-private sector alliance to address human trafficking in South-East Asia supply chains.

Wal-Mart did not immediately respond to detailed USA TODAY messages seeking comment. However, Costco said agreements with its suppliers "prohibit, among other things, use of slave labor and other violations of labor law."

"We are committed to working with our suppliers of Thai shrimp to require them to take corrective action to police their feedstock sources with respect to poor labor practices," said Costco. "This commitment so far has involved visits by our buying staff to Thailand and discussions with the Thai government, our suppliers, and other industry participants."

Thailand is the world's top global exporter of shrimp, according to a 2012 report by the International Labour Organization, which promotes work rights and human rights. The Southeast Asian country produced more than 202,000 metric tons of raw shrimp in 2011, with the U.S. the top importer of the seafood, the report said.

Thailand's government, along with the ILO, U.S. Department of Labor and other groups, is conducting a four-year project aimed at ensuring that "enterprises throughout the shrimp and seafood processing industry supply chain comply with national labor laws and international labor standards, in particular those relating to child labor and forced labor."