Location data can be a contentious subject, especially when it comes to who has access to it. Where that data goes beyond, say, a wireless carrier, is important. And now the United States Federal Communications Commission (FCC) is demanding more information regarding that data from the biggest wireless carriers in the U.S.

Motherboard has the report on Wednesday. According to the publication, FCC Commissioner Jessica Rosenworcel is now asking the heads of each of the four major wireless carriers (AT&T, Sprint, T-Mobile, and Verizon) if third-party data aggregators were able to save phone location data. What’s more, Rosenworcel wants to know what these carriers are doing to make sure that the phone location data sold to these companies is deleted.

“Real-time location information is sensitive data deserving the highest level of privacy protection. But it is evident from press reports that this data may have been sold without the explicit consent of consumers and without appropriate safeguards in place.

Accordingly, I appreciate your decision to end these location aggregation services by March of this year. To that end, I kindly request that you provide an update on your efforts and confirm by what date AT&T ended its arrangements to sell the location data of its customers. Please also confirm whether and by what date the company ended arrangements to sell assisted or augmented GPS data.

Finally, the public still has very little detail about how much geolocation data is being saved and stored-including in ways that may be far too accessible to others. Even de-anonymized location data may be combined with other information in ways that could make it personally identifiable again. Accordingly, please explain whether AT&T’s agreements permitted aggregators or others to save and store location data they received from your company. If so, please confirm what steps your company is taking to ensure that these companies delete or destroy previously shared data and any derivative data. Alternatively, please explain what steps AT&T is taking to safeguard such data from use or onward sale that is inconsistent with consumers’ original content.”

This is in connection to a report that was released back in January of this year. In that story, we learned that major wireless carriers sell phone location data to a variety of sources. The wireless carriers were handing the data over to companies like Zumigo and LocationSmart, who were then selling the data off. That put the customer’s phone location data out there in the wild, and easily accessible by bounty hunters looking to obtain the information.

At this point, all of the major wireless carriers have pledged to stop this practice. However, some carriers have been better at this promise than others, as some were still doling out customer phone location data in early February.

The wireless carriers are tasked with responding to the FCC Commissioner’s request for a statement by May 15 of this year.