(Reuters) - Lawyers for Wal-Mart Stores Inc (WMT.N) have flagged Brazil, China, India and South Africa in addition to Mexico, as countries that represent the highest corruption risk in a global review, according to a letter from lawmakers investigating the company.

The lawyers said they first reviewed Wal-Mart policies in Mexico, Brazil and China, and later recommended the company also evaluate its operations in India and South Africa. The lawyers referred to those five countries as regions where the risk was the greatest, according to the lawmakers.

The company has acknowledged it is investigating bribery allegations involving its Mexican operations, and that it initiated a world-wide review of its anti-corruption compliance program in March 2011, but has not provided details about the review.

According to the letter, from Representatives Elijah Cummings and Henry Waxman, both Democrats, Wal-Mart continued to review its anti-corruption policies in other countries.

The review led Wal-Mart to revise its program to include a new procedure for escalating corruption complaints to senior management and the board's audit committee, the letter said.

Cummings and Waxman, who are the ranking members, respectively, of the House Oversight and House Energy committees, asked the company on Tuesday to provide documents about the review and the recommendations.

The pair wrote to Wal-Mart Chief Executive Michael Duke and also asked him to allow certain witnesses to cooperate with a congressional investigation into the bribery allegations.

"We are cooperating with the ongoing federal investigations, and as appropriate, will also continue to assist Members of Congress and their staffs in understanding our efforts to address FCPA issues," Wal-Mart spokesman David Tovar said in a statement.

Outside lawyers for Wal-Mart at two law firms, Greenberg Traurig and Akin Gump Strauss Hauer & Feld, briefed the lawmakers on May 21 about the company's program to comply with the Foreign Corrupt Practices Act, a 1970s-era law that bars bribes to officials of foreign governments.

But the lawyers did not answer any questions about the substance of the bribery allegations, which were brought to light in an April 21 New York Times report that said that management at Wal-Mart de Mexico (WALMEXV.MX) orchestrated bribes of $24 million to help it grow quickly in the last decade and that Wal-Mart's top brass tried to cover it up.

The two lawmakers have previously expressed frustration about the information they have received from Wal-Mart.

While Wal-Mart has tapped the brakes on its growth in Brazil and China, last month Walmart International CEO Doug McMillon said the slowdown was not a result of foreign bribery concerns.

Lawyers for Wal-Mart are scheduled to brief Congressional investigators on Wednesday about the "investigative protocols" the company is using to examine bribery allegations in Mexico, according to the letter.

(Reporting By Aruna Viswanatha in Washington and Jessica Wohl in Chicago; Editing by John Wallace, Tim Dobbyn and Bernard Orr)