NEW YORK (CNN/Money) - A U.S. federal grand jury is investigating allegations of misspending within Wal-Mart by its former vice chairman Tom Coughlin after the retailer recently revealed that it had suspended his compensation benefits amid an internal probe into misuse of company funds.

News reports quoting a company spokesperson Friday said the jury's investigation was spurred when it handed over internal documents to the Justice Department.

"We are aware that a grand jury is looking into the matter and are cooperating fully," Wal-Mart spokeswoman Christi Gallagher said a statement emailed to CNN/Money.

Thomas Coughlin, who was vice chairman of Wal-Mart's board and formerly held the title of president of Wal-Mart Stores, resigned from the world's largest retailer in March after Wal-Mart found what it said was a pattern of expense-account abuses and the use of false invoices to obtain reimbursements.

Following his resignation, accusations emerged that Coughlin may have used undocumented expense payments of as much as $500,000 to pay for anti-union activities.

Last week, the United Food and Commercial Workers (UFCW) union filed a complaint against Wal-Mart Stores asking the National Labor Relations Board to investigate whether the retailer "bribed" employees to block union activities.

Subsequently, Wal-Mart disclosed in a filing with the Securities & Exchange Commission that the company has suspended a string of compensation benefits to Coughlin amid an investigation into the matter.

The company's proxy showed that Coughlin's bonus compensation for last fiscal year was set at $2.9 million. His salary totaled $1.03 million, up from $983,894 in the prior fiscal year, according to the filing.