A report says that e-commerce giant Amazon adjusted its product search results to emphasize items that are more profitable to the company.

The Wall Street Journal reported Monday that Amazon late last year changed its secret algorithm that ranks search results to lift more profitable items. The change to the search algorithm could steer customers toward Amazon private-label products that deliver higher profit margins than competing listings, the Journal reported.

Digital giants including Amazon, Apple, Google and Facebook are under scrutiny for how they govern their online platforms. The companies have been accused of favoring their own products over those of rivals, potentially stifling competition.

Amazon didn’t respond to requests for comment. A spokeswoman told the Journal that Amazon has long considered long-term profitability, but that it didn’t make decisions based solely on that metric.

A team of Federal Trade Commission investigators has begun interviewing small businesses that sell products on Amazon to determine whether the e-commerce giant is using its market power to hurt competition. A House panel investigating big tech companies for potential antitrust violations is seeking information from customers of Amazon, Apple, Google and Facebook about the state of competition in digital markets and the adequacy of existing enforcement.