Amazon’s lead data regulator in Europe, Luxembourg’s National Commission for Data Protection, has raised privacy concerns about its use of manual human reviews of Alexa AI voice assistant recordings.

A spokesman for the regulator confirmed in an email to TechCrunch it is discussing the matter with Amazon, adding: “At this stage, we cannot comment further about this case as we are bound by the obligation of professional secrecy.” The development was reported earlier by Reuters.

We’ve reached out to Amazon for comment.

Amazon’s Alexa voice AI, which is embedded in a wide array of hardware — from the company’s own brand Echo smart speaker line to an assortment of third-party devices (such as this talkative refrigerator or this oddball table lamp) — listens pervasively for a trigger word which activates a recording function, enabling it to stream audio data to the cloud for processing and storage.

However, trigger-word activated voice AIs have been shown to be prone to accidental activation. A device may be being used in a multi-person household, so there’s always a risk of these devices recording any audio in their vicinity, not just intentional voice queries…

In a nutshell, the AI’s inability to distinguish between intentional interactions and stuff they overhear means they are natively prone to eavesdropping — hence the major privacy concerns.

These concerns have been dialed up by recent revelations that tech giants — including Amazon, Apple and Google — use human workers to manually review a proportion of audio snippets captured by their voice AIs, typically for quality purposes — such as to try to improve the performance of voice recognition across different accents or environments. But that means actual humans are listening to what might be highly sensitive personal data.

Earlier this week Amazon quietly added an option to the settings of the Alexa smartphone app to allow users to opt out of their audio snippets being added to a pool that may be manually reviewed by people doing quality control work for Amazon — having not previously informed Alexa users of its human review program.

The policy shift followed rising attention on the privacy of voice AI users — especially in Europe.

Last month thousands of recordings of users of Google’s AI assistant were leaked to the Belgian media, which was able to identify some of the people in the clips.

A data protection watchdog in Germany subsequently ordered Google to halt manual reviews of audio snippets.

Google responded by suspending human reviews across Europe, while its lead data watchdog in Europe, the Irish DPC, told us it’s “examining” the issue.

Separately, in recent days, Apple has also suspended human reviews of Siri snippets — doing so globally, in its case — after a contractor raised privacy concerns in the U.K. press over what Apple contractors are privy to when reviewing Siri audio.

The Hamburg data protection agency which intervened to halt human reviews of Google Assistant snippets urged its fellow EU privacy watchdogs to prioritize checks on other providers of language assistance systems — and “implement appropriate measures” — naming both Apple and Amazon.

In the case of Amazon, scrutiny from European watchdogs looks to be fast dialing up.

At the time of writing it is the only one of the three tech giants not to have suspended human reviews of voice AI snippets, either regionally or globally.

In a statement provided to the press at the time it changed Alexa settings to offer users an opt-out from the chance of their audio being manually reviewed, Amazon said: