NEW YORK - Mexico's federal government should investigate allegations of a vast bribery campaign by top executives of Wal-Mart's Mexican subsidiary to build stores across the country, the head of a watchdog group said Sunday.

Eduardo Bohorquez, director of Transparencia Mexicana, said international conventions obligate Mexico's government to get involved even though only local officials have been accused in the scandal.

Government officials have not commented on the allegations contained in a New York Times report published Saturday that said Wal-Mart Stores Inc. failed to notify law enforcement after its own investigators found evidence that millions of dollars in bribes had been paid in Mexico to spur the company's rapid expansion there.

One of every five Wal-Mart stores now is in Mexico and it is that country's largest private employer, with 209,000 employees there.

The Times said Wal-Mart shut down its internal probe despite a report by its lead investigator that Mexican and U.S. laws likely were violated by executives of its biggest foreign subsidiary, Wal-Mart de Mexico.

In recent years, the U.S. government has stepped up enforcement of the 1977 Foreign Corrupt Practices Act, which bars U.S. companies from bribing foreign government officials or companies to secure or retain business.

Numerous corporations have been ensnared by the law, including Johnson & Johnson, which agreed last year to pay $70 million to settle charges that it bribed doctors in Europe and paid kickbacks to the Iraqi government.

Avon Products Inc. fired its vice chairman in January as part of a long-running probe into allegations that bribes were paid in China. A former chief executive of engineering and construction firm KBR Inc. was sentenced to 2 1/2 years in prison in February for bribing officials in Nigeria to win contracts.

Last month, Mexican authorities announced that they were investigating allegations that a U.S. aviation company paid bribes to secure contracts to maintain government aircraft.

Mexico's Attorney General's Office said the probe involved six officials at two federal agencies and two state governments who allegedly took bribes from Oklahoma-based BizJet International Sales and Support Inc. in exchange of work contracts. Prosecutors said the case involved about $2 million in bribes for contracts worth at least $24 million.

The office gave no other details about the case, but the U.S. Department of Justice said BizJet had agreed to pay an $11.8 million fine to settle a corruption case that alleges its employees bribed government officials in Mexico and Panama to secure maintenance contracts.

The Justice Department said that Bizjet employees between 2004 and 2010 paid bribes to officials at Mexico's Federal Police, the Mexican President's Fleet, the air fleets for the Mexican states of Sinaloa and Sonora and Panama's Civil Aviation Authority.