The chairman of U.S. Federal Trade Commission said Wednesday that the agency is “very interested” in learning more about the European Union’s record fine of Google.

The comments by a top U.S. antitrust enforcer at a House subcommittee hearing came just hours after the EU levied a $5 billion (4.3 billion euro) fine on the Alphabet Inc. company, ordering it to change the way it puts search and web browser apps on Android devices.

“We’re going to read what the EU put out very closely,” said FTC Chairman Joseph Simons, while noting the U.S. and EU have different antitrust regimes. He said he had discussed the issue Tuesday with EU Competition Commissioner Margrethe Vestager.

Earlier in the hearing, which featured all five FTC commissioners, Simons said the mobile operating system market dominated by Android and Apple Inc.’s iOS is “concentrated.”

“In the antitrust world, most of the problematic conduct occurs where firms are big and have market power,” Simons said. “This is one of the places we would focus.”

He added Google and Apple do “compete pretty heavily against each other.”

The chairman, who took over in May, plans to hold a series of public hearings about the agency itself. He has said the question of whether tech firms such as Google, Facebook Inc. and Amazon.com Inc. are undermining competition will be a priority.

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