U.S. antitrust regulators are investigating whether Google unit Motorola Mobility is living up to licensing commitments made when its patents were adopted as industry standards, two people familiar with the probe said on Friday.

The Federal Trade Commission sent civil investigative demands, essentially civil subpoenas, to companies this week asking them about Motorola Mobility's licensing practices, one person said.

The industry standards affected have to do with Wi-Fi and video standards, one of the people said.

Motorola Mobility has sued Microsoft Corp for infringement of industry standard patents and asked for its Xbox product to be barred from the U.S. market.

Standard-setting bodies meet periodically to determine which technology will be used industry-wide, which ensures devices will work together. Companies who hold those patents commit to licensing them broadly and on reasonable terms, even to competitors.

"We take our commitments to license on fair, reasonable and non-discriminatory terms very seriously," a Google spokeswoman said in an email when asked about the probe.

A spokeswoman for Microsoft confirmed receipt of the FTC inquiry but declined to describe what was in it. Apple Inc declined comment on whether it received a similar inquiry.

The FTC declined to comment.

The FTC also has a broader investigation underway into whether Google distorts its search results to steer people to its related businesses, like Google Places. The agency recently hired a big name litigator, Beth Wilkinson, to lead its probe.

Bloomberg was the first to report the Motorola patent investigation on Friday.