Google acknowledged its contractors are able to listen to recordings of what people say to the company’s artificial-intelligence system, Google Assistant.

The company admitted on Thursday that humans can access recordings made by the Assistant, after some of its Dutch language recordings were leaked. Google is investigating the breach.

The recordings were obtained by the Belgian public broadcaster VRT, which reviewed more than 1,000 audio clips and found 153 had been captured accidentally.

Google Assistant begins automatically recording audio when prompted by a user, usually by saying a wake-up word or phrase like, “OK, Google”.