Wal-Mart on Thursday reported that its investigation into violations of a federal antibribery law had extended beyond Mexico to China, India and Brazil, some of the retailer’s most important international markets.

The disclosure, made in a regulatory filing, suggests Wal-Mart has uncovered evidence into potential violations of the Foreign Corrupt Practices Act, as the fallout continues from a bribery scheme involving the opening of stores in Mexico that was the subject of a New York Times investigation in April.

The announcement underscores the degree to which Wal-Mart recognizes that corruption may have infected its international operations, and reflects a growing alarm among the company’s internal investigators. People with knowledge of the matter described how a relatively routine compliance audit rapidly transformed into a full-blown investigation late last year — involving hundreds of lawyers and three former federal prosecutors — when the company learned that The Times was examining problems with its operations in Mexico.

A person with direct knowledge of the company’s internal investigation cautioned that Thursday’s disclosure did not mean Wal-Mart had concluded it had paid bribes in China, India and Brazil. But it did indicate that the company had found enough evidence to justify concern about its business practices in the three countries — concerns that go beyond initial inquiries and that are serious enough that shareholders needed to be told.