A group of Democratic senators is asking the FBI to investigate an alleged cyberattack on the Federal Communications Commission (FCC) website earlier this month.

In a letter to acting FBI Director Andrew McCabe sent Wednesday, the senators asked the bureau to “investigate the source” of the distributed denial-of-service (DDoS) attack.

“Any cyberattack on a federal network is very serious,” Democratic Sens. Brian Schatz (Hawaii), Al Franken (Minn.), Patrick Leahy (Vt.), Ed Markey (Mass.), and Ron Wyden (Ore.) wrote.

{mosads}“This particular attack may have denied the American people the opportunity to contribute to what is supposed to be a fair and transparent process, which in turn may call into question the integrity of the FCC’s rulemaking proceedings,” they wrote.

The FCC on May 8 claimed that its electronic filing system was a victim of “multiple” DDoS attacks, which occur when hackers take down a website by overloading it with an enormous amount of traffic. 

The alleged attack occurred after comedian John Oliver directed viewers of his HBO show to file comments on the agency’s website in support of its net neutrality rules, amid an effort by the new GOP chairman to roll back the Obama-era regulations. 

Many had attributed the website’s slowdown to the volume of comments produced by Oliver’s segment, but the FCC instead blamed malicious actors days later.

“These were deliberate attempts by external actors to bombard the FCC’s comment system with a high amount of traffic to our commercial cloud host,” FCC chief information officer David Bray said in a statement then. 

Fight for the Future, a pro-net neutrality group, expressed skepticism of the FCC’s claim, citing a lack of evidence. Wyden and Schatz have already requested more information from the agency about its DDoS claim. 

In the Wednesday letter to McCabe, the senators asked to be briefed by the FBI on the matter by June 23.

“We ask that the FBI prioritize this matter and investigate the source of this attack,” they wrote.