The Federal Trade Commission is taking a closer look at Twitter, sending a query recently to another tech firm that has sparred with the social-networking site.

UberMedia, which makes products allowing users to access Twitter from mobile phones, confirmed Thursday that it was contacted by the FTC about Twitter. The company declined to give specifics about the inquiry, but UberMedia has fought with Twitter in recent months about whether it can continue offering Twitter-related apps.

As Twitter has exploded into a global phenomenon, an ecosystem of products built by outside developers on its platform has sprung up. Critics say the company is trying to control these start-ups and potentially quash them.

The FTC and Twitter declined to comment. The FTC’s involvement was first reported Thursday by the Business Insider.