Wal-Mart Stores, Inc. (NYSE:WMT) could eventually face a heavy fine from the Securities and Exchange Commission over allegations last year that its employees in Mexico bribed officials to boost its business, according to one former SEC attorney.

Jordan Thomas, who previously worked on enforcement in major SEC cases involving Enron, UBS AG (VTX:UBSN), and Citigroup Inc. (NYSE:C), told International Business Times that any potential fine is likely to be significant.

The SEC declined to comment to IBTimes on any potential ongoing investigation, as per its usual policy, but Thomas said there’s no serious doubt that such an investigation is happening.

The Department of Justice has opened a criminal probe into the matter, which intensified after a comprehensive New York Times report uncovered evidence of bribery abroad by the world’s largest retailer.

WalMart itself actually opened an internal investigation before the Times’ report, and also noted that the alleged bribery happened over six years ago.

In April 2012, after the report, the company reiterated its commitment to anticorruption laws, and said it was cooperating with federal investigators.  

“What is maybe open is who is responsible, and what’s the price that WalMart is going to have to pay,” said Thomas, who worked as assistant enforcement director at the SEC and is now in private practice.

“My bet is that it’s going to be quite significant,” he continued.

“If you believe the New York Times story, it [misconduct] was endemic, and they had senior people involved, over long periods of time…And it also had a significant market impact,” he said.

Securities laws often require any ill-gotten gains to be returned as part of a civil penalty, continued Thomas.

Thomas declined to estimate the size of any potential fines, which would likely come under the auspices of the Foreign Corrupt Practices Act, a securities law prohibiting bribery overseas by representatives of U.S. companies.

Thomas also doesn’t have any firsthand knowledge of the matter.

It could be years before any actual fines are announced or investigations concluded, with typical SEC investigations taking two to four years or longer.  

The largest previous settlement under the FCPA came in 2008, after Siemens AG (FRA:SIE) paid $800 million to the Department of Justice and the SEC to settle allegations that the German company paid bribes to government officials in several countries.

In its latest quarterly report, WalMart said it expects expenses of $75 to $80 million for the next six months, in compliance and FCPA costs.

One UBS analyst noted last year that recent FCPA fines have settled between 1 to 2 percent of the firm’s total revenue, meaning WalMart could be on the hook for billions.

But law professor Mike Koehler of the Southern Illinois University law school has said on his widely read FCPA law blog that WalMart’s fines will probably not land within top five FCPA enforcement penalties of all time, because the heaviest fines to date have involved procurement cases, not permit or license cases.

In an earlier paper, Koehler, an anti-corruption expert, called estimates that WalMart could face over $10 billion in ultimate fines and penalties “wildly speculative.”