More than 1,000 recordings were obtained by Belgian broadcaster VRT NWS, which noted that some contained sensitive personal conversations as well as information that identified the person speaking.
Facebook said audio snippets reviewed by contractors were masked so as not to reveal anyone's identity. It said it stopped the practice a week ago. The development was reported earlier by Bloomberg.
Google said it suspended doing this worldwide while it investigates the leaks. Amazon said it still uses humans, but users can decline, or opt out, of the human transcriptions. Published reports say Apple also has used humans, but has stopped.
Irish data-protection regulators say they're seeking more details from Facebook to assess compliance with European data regulations.
Facebook is already under scrutiny for a variety of other ways it has misused user data. It agreed to a $5 billion fine to settle a US Federal Trade Commission probe of its privacy practices.