ALEXANDRIA, Va.—The U.S. Department of Justice is investigating whether Mastercard Inc. has acted in an anticompetitive manner in its debit-card business, Bloomberg reports. It’s a sign that the DOJ probe, previously centered on Visa, has widened.

Mastercard said it received a civil investigative demand from the department last month seeking documents regarding a potential violation of certain sections of the Sherman Act, according to Bloomberg.

“It’s not surprising that the DOJ would request information from other players in the debit space,” Mastercard chief financial officer Sachin Mehra said. “It’s hard to speculate about the potential outcome, but these types of investigations do take a number of years.”

The inquiry involves a 2010 law known as the Durbin Amendment that requires banks to include two competing networks on their debit cards. Smaller networks such as Pulse, Star, and NYCE can be less expensive for merchants.

The Durbin Amendment has saved merchants billions of dollars a year in swipe fees, with 70% of thesavings passed on to consumers, according to studies.

At the NACS SOI Summit in Dallas last week, it was revealed that the convenience industry spent $19.5 billion in 2022 in swipe fees, a sum that has increased 82% in the past three years.