The US Department of Justice is investigating whether Visa Inc is engaging in anticompetitive practices in the debit-card market, the Wall Street Journal reported on Friday, citing people familiar with the matter.
The department's antitrust division has been probing if Visa limited merchants' ability to route debit-card transactions over card networks that are often less expensive, the WSJ reported.
Many of the department's questions are focused on online debit-card transactions, but investigators are looking into in-store issues as well, according to the report.
Visa declined to comment. The Justice Department did not immediately respond to a Reuters request for comment.
Earlier this year, Visa and fintech startup Plaid called off their $5.3 billion merger following a lawsuit from the Justice Department aimed at blocking the deal on antitrust grounds.
The Justice Department had argued that the deal "would eliminate a nascent competitive threat" to Visa, which it said was a "monopolist in online debit transactions".
The new probe is also examining if the payment processor's practices are allowing it to maintain a dominant market share unlawfully, according to the report.