A U.S. antitrust regulator has opened a formal probe into whether Google’s Motorola Mobility unit is honoring pledges it made to license industry- standard technology for mobile and other devices on fair terms, Bloomberg reported citing three people familiar with the situation.

The Federal Trade Commission has issued a civil investigative demand, which is similar to a subpoena, to the owner of the Android mobile operating system as it scrutinizes whether Google is improperly blocking rivals’ access to patents for key smartphone technology, one of the people said.

The agency is also seeking information from companies including Microsoft and Apple as it investigates whether Google intends to license technology under patents that help operate 3G wireless, Wi-Fi and video streaming on fair and reasonable terms, another one of the people said. The people declined to be identified because they weren’t authorized to speak publicly about the matter.

Another focus of the FTC probe, the person said, is Google’s decision to continue litigation started by Motorola Mobility over industry-standard patents before Google bought the company. Those lawsuits could end up blocking imports of popular consumer products such as Microsoft’s Xbox and Apple’s iPhone and iPad.

U.S. antitrust regulators have agreed the FTC will focus on Motorola Mobility and the Justice Department will scrutinize Samsung Electronics Co.’s handling of industry-standard patent claims, said another person familiar with the matter. The person didn’t know if the Justice Department has issued information demands in connection with its review of Samsung.

The FTC is already conducting a broad antitrust investigation into whether Google’s search-results rankings and other business practices harm competition.

Earlier this month, the FTC filed a statement with the ITC, which is charged with protecting U.S. markets from unfair trade practices, suggesting that companies should be limited in their ability to win orders blocking imports of competitors’ products over the use of patents built into industry-wide standards.

The ITC said June 26 it would review whether Apple, which gets about 75 percent of its revenue from the iPhone, iPad and related products, infringed four patents held by Motorola Mobility. A trade judge in April said Apple infringed one of the patents.

Should the ITC side with Motorola Mobility, the agency has the power to order U.S. Customs and Border Protection to stop iPhones and iPad computers made in Asia from entering the U.S. On July 2, the ITC is scheduled to announce whether it will review a trade judge’s findings that Microsoft’s Xbox gaming system infringes four of five Motorola Mobility patents.