What caused the crash of the Federal Communications Commission’s online comment-filing system? The FCC is blaming denial-of-service attacks from “external actors” without explicitly laying any blame on comedian John Oliver’s latest story about net neutrality. Now, some Senators want to know what happened.

In a letter [PDF] to FCC Chair Ajit Pai, Senators Ron Wyden (OR), and Brian Schatz (HI) point out that any denial-of-service attack against a federal agency is a threat, “doubly so if the attack may have prevented Americans from being able to weigh in on your proposal to roll back net neutrality protections.”

Worried about the possibility that people might be shut out of filing comments, the lawmakers are asking the FCC to create alternative options for submitting their thoughts on this issue. When the previous go-around with net neutrality crashed the FCC’s site in 2014, the Commission created a special email address for submitting comments.

Additionally, the Senators ask Pai to respond to a series of questions about the nature of the attack — how many devices were involved; were people blocked from commenting; how many visitors can the commenting site handle at one time; were comments lost — and any evidence it may have about the source. The letter also wants to know if the FCC has sought and received any help from other federal agencies in regard to these sorts of attacks, and whether the Commission is prepared if such an attack happens again.

The letter gives Pai until June 8 to respond.