Nine managers at Whole Foods stores in Maryland, Virginia and the District have been fired for manipulating a store bonus program, a spokesman for the grocery chain said Wednesday.

As first reported by the Associated Press, the managers, at nine separate Whole Foods stores, were fired for manipulating the chain’s “Gainsharing” program. The program awards bonuses to employees whose departments come in under budget.

“As productivity increases, then all the people at our stores make more money,” Whole Foods chief executive John Mackey said in a 2004 interview with Grist. “It doesn’t flow down the bottom line, it flows into higher paychecks.”

Austin-based Whole Foods declined to offer details on the nature of the ma­nipu­la­tion or say which locations were affected, saying the incident was still under investigation and “isolated” to a relatively small number of its 457 stores.

“We took swift action, but, relative to the rest of the company, this manipulation only happened in nine of our locations,” spokeswoman Brooke Buchanan said.

“Gainsharing” has been criticized as a way for companies to identify ways to cut labor costs, rewarding workers in the short term but potentially eliminating jobs in the long term. Workers who filed a federal lawsuit against Whole Foods in 2012 alleged that the bonus program’s payments were too low. The suit settled that same year.