The senators, who serve as chair and ranking member of the Judiciary Subcommittee on Privacy, Technology and the Law, specifically referenced in their letter a widely reported incident last month in which a Portland couple had their conversation recorded by the Alexa voice-recognition software used in the Echo. The device then sent the recording as an attachment to one of their contacts without them requesting it.

Amazon confirmed that the event occurred, and explained that it was caused by a series of unlikely triggers. In their letter to Bezos, the senators demanded action that would prevent the same thing from happening again.

The letter contained almost 30 questions, including about some of the nitty-gritty of Alexa’s data management like when Alexa sends data to Amazon’s servers, how often it does so, how long that captured data is stored, and what period of time after someone says “Alexa” (which cues the technology to perk up) does an Echo record a conversation. The senators also asked whether consumers can delete recordings.

Wired first reported about the letter.

All voice-recognition devices—whether those from Apple, Amazon, Google, or startups—must listen continuously in order to know when its trigger is hit. (On smartphones, a user may opt to use a different trigger.) While Amazon and Google have characterized their respective systems’ privacy components relatively thoroughly, with Apple erring on the side of sending relatively little voice data off of devices, Amazon’s particulars are less well known.

Update: This story has been updated with link to the senators’ letter.