The US Senate Commerce Committee—which has jurisdiction over media issues, consumer protection issues, and internet communication—has sent a letter to Mark Zuckerberg requesting answers to questions it has on its trending topics section. The letter comes after Gizmodo on Monday reported on allegations by one former news curator, who worked for Facebook as a contractor, that the curation team routinely suppressed or blacklisted topics of interest to conservatives. That report also included allegations from several former curators that they used a “injection tool” to add or bump stories onto the trending module.

The letter asks that Facebook “arrange for your staff including employees responsible for trending topics to brief committee staff on this issue.” The letter was signed by Chairman for the Committee on Commerce, Science, and Transportation, Senator John Thune (R) from South Dakota.