Twitter executives flocked to Capitol Hill on Thursday to meet with congressional investigators in a bid to address mounting concerns about how interference from Russian state agents on the platform may have affected the outcome of the 2016 presidential election. In recent weeks, much of the focus of special counsel Robert Mueller’s investigation has shifted to social media, with Mark Zuckerberg now in the hot seat for disclosing that Facebook sold some 3,000 ads between 2015 and 2017 to a pro-Kremlin troll farm. In recent days, that focus has seemingly shifted to Twitter and C.E.O. Jack Dorsey, particularly after a report that foreign actors ran Twitter accounts posing as Americans and used Twitter bots to spread news stories about leaked e-mails from Democratic operatives. After its meeting with lawmakers on Thursday, Twitter published a blog post noting that it had suspended 201 Twitter accounts related to Russian-linked sources that had also posted ads on Facebook. “Neither the original accounts shared by Facebook, nor the additional related accounts we identified, were registered as advertisers on Twitter,” the company wrote. “However, we continue to investigate these issues, and will take action on anything that violates our Terms of Service.”

The contrite mea culpa, however, was not enough to placate the furor of some congressional investigators. Virginia Senator Mark Warner, the top Democrat on the Senate intelligence Committee, told reporters that Twitter’s presentation had been “deeply disappointing,” and that the company needs to answer more questions. “Their response was frankly inadequate on almost every level,” Warner said. “I’m more than a bit surprised that anyone from the Twitter team would think that the presentation they made to the Senate staff today even began to answer the kind of questions we’d asked. So there is a lot more work they need to do.” Warner’s cardinal beef was that Twitter performed a limited search of its records based on information that Facebook had already revealed during its investigation. “The notion that their work was basically derivative, based upon accounts that Facebook had identified, showed an enormous lack of understanding from the Twitter team of how serious this issue is, the threat it poses to democratic institutions, and again, begs many more questions than they [answer],” he continued.

The House Intelligence Committee is hoping to hold its own hearing next month. Adam Schiff, the panel’s top Democratic lawmaker, has urged Twitter to take the probe more seriously, and to determine more precisely the extent to which Russian state actors may have interfered on its platform during the election. “At this early stage in their internal review, Twitter has identified and taken remedial steps against accounts linked to Russian government actors,” Schiff said. “Much of the information that Twitter used to identify Russian-linked accounts, however, was derived from Facebook’s own analysis, and it is clear that Twitter has significant forensic work to do to understand the depth and breadth of Russian activity during the campaign.”

Twitter will have another opportunity to disclose more information later this year. Executives from Twitter were also invited to testify in an open hearing before the Senate Intelligence Committee in November, alongside executives from Facebook and Google parent company Alphabet, about how their platform may have been used to sway the election. But some in Silicon Valley question the company’s incentives for veracity. Twitter, after all, is being torn between its patriotic duty and investor relations. The company, which averages about 300 million monthly active users, has for years faced pressure to crack down on trolls and bots among its consumer base. Some wonder just how far that figure would fall if it actually did adequately police itself.