The Federal Communications Commission yesterday opened an inquiry into whether Google’s phone-management service Google Voice is restricting calls.

Google Voice allows people to link all of their phones to a common number and to manage calls and messages through a single Web site. The service can also be used to send and receive phone calls and text messages.

The search-engine giant reserves the right to restrict outgoing calls to some phone numbers, including adult chat lines and conference-call centers, which charge higher access fees to carriers. Blocking such calls reduces Google’s expenses for the service.

The FCC’s letter asked how Google Voice identifies phone numbers that are restricted and how it notifies customers of those restrictions.

The company said it blocks calls to certain local phone numbers because “they charge exorbitant termination rates” and “partner with adult sex chat lines and ‘free’ conference calling centers to drive high volumes of traffic.”

Phone giant AT&T has said Google violates rules designed to ensure phone companies connect all calls, and a group of lawmakers this week asked the FCC to investigate the matter, saying the practice could hurt rural customers.