Republican Senator Orrin Hatch of Utah on Thursday asked US Federal Trade Commission Chairman Joseph Simons to reexamine Google’s conduct in search and digital advertising, saying reports of potentially anticompetitive conduct are “disquieting.”

The move steps up pressure on Google after Trump lashed out at the company for what he claimed are rigged search results that favour liberal over conservative news outlets. The president also criticised Facebook Inc. and Twitter Inc., joining a chorus of conservatives who claim internet companies favour liberal viewpoints.

Google declined to comment on Hatch’s letter. After Trump’s attack this week, the company said its search function is not used to set a political agenda and isn’t biased against any ideology.

The FTC previously investigated Google over whether the company skewed search results to favour its own services. The agency closed the case in 2013 without bringing an enforcement action after Google agreed to stop certain practices, including removing restrictions on the use of its online search advertising platform.

The decision to close the case, made under the administration of former President Barack Obama, disappointed some companies and consumer groups who claimed Google abused its dominance. The FTC is now led by Simons, who has expressed a willingness to examine the conduct of technology platforms.

“In the past, Google has offered arguments that its conduct is procompetitive,” Hatch wrote. “But much has changed since the FTC last looked at Google’s conduct regarding search and digital advertising.”