It was just a few months ago that the Federal Communications Commission issued a rebuke to cable giant Comcast Corp. over its efforts to control the flow of Internet traffic over its network. The company was ordered to change its practices to keep in line with federal policies that say everyone should be treated equally on the Internet.

The FCC decided that Comcast went too far when it blocked the high-volume traffic of some subscribers. The company was trying to deal with the file-sharing traffic that tends to hog a large portion of network capacity.

But now the FCC is questioning what appears to be preferential treatment being given to users of Comcast’s digital voice service. In a letter sent to Comcast on Sunday, the FCC asked for clarifaction on network management practices.

Comcast previously told the FCC that its traffic managment system would cause high-volume users to experience choppy connections when using Internet-based phone services (VoIP). Sunday’s letter asks why Comcast’s own VoIP customers are told that they will not experience those same choppy connections. The company has until Jan. 30 to respond.

The FCC inquiry drew applause from Internet advocacy group Free Press, which has filed complaints against Comcast and its efforts to manage network traffic.

From Ben Scott, the group’s policy director:

“This letter is a positive sign that the FCC’s Comcast decision was not a one-and-done action on Net Neutrality…An open Internet cannot tolerate arbitrary interference from Internet service providers. Congress and the FCC must close any legal loopholes that permit anti-competitive behavior to thrive.”