US House of Representatives’ committee on energy and commerce has sent a letter to John Hanke, CEO of Niantic, Inc.—the maker of the game Pokémon Go under a license from Nintendo—inquiring about the impact of the game on consumers’ mobile data usage: “We are writing to better understand what measures Niantic has undertaken to ensure consumers are informed of Pokémon Go’s effect on their mobile data usage. Pokémon Go became the biggest mobile game in U.S. history, having been downloaded approximately 7.5 million times in the U.S. within a week of its launch and earning an estimated $2.3 million a day on the iOS and Android platforms. While Pokémon Go has been highly successful, the game has raised concerns. In addition to issues related to the game being played in inappropriate locations, safety, and privacy, recent reports suggest that playing Pokémon Go could exhaust a consumer’s available monthly mobile data.”

— T-Mobile CEO John Legere: In just four days, the number of Pokémon Go users on the carrier’s network had doubled, and their data usage had quadrupled. Users have reported maxing out their monthly data usage plans within a week of playing and have complained eating through and entire family plans within few days of playing.

— The letter comes despite reports that the program does not use up large amounts of wireless data as compared to other social media, video and music streaming products. According to a Wall Street Journal report, network analytics firm P3 Communications Inc. says the app only uses around five to 10 megabytes of data per hour. “That’s tiny compared with the 350 megabytes consumed by watching an hour of HD video, according to Verizon’s data calculator.”