Amazon Echo device recorded a couple's private conversation and sent it to one of their contacts, igniting new privacy concerns about the voice-activated gadgets.

The two found about it when they received a phone call two weeks ago from one of the husband's employees telling them to "Unplug your Alexa devices right now. You're being hacked," news station KIRO 7 reported. Amazon.com Inc. said in a statement to the station that it was an "extremely rare occurrence."

According to Amazon, the Echo woke after hearing a word in the couple?s conversation that sounded like "Alexa" -- the usual trigger to begin recording. The speaker later heard "send message" during the conversation, at which point the device asked, "to whom?" The pair continued talking in the background and the Echo?s system interpreted part of the chat to identify a name in the couple?s contact list. Alexa then asked aloud if they wanted to send a message to that contact and heard "right" in more background conversation.

The couple used Amazon's voice-activated devices throughout their home to control heat, lights and the security system, according to the news report.

There have been many reports that Alexa users were hearing random, unprompted laughter from the voice-activated assistant. And last month, security researchers said they found a way to make Alexa listen to users indefinitely -- and provide a transcript of everything it heard. Amazon said it patched that loophole.

These incidents, along with the new potential use cases for AI-powered assistants highlighted by Google Duplex, have raised questions about the level of privacy consumers can and should expect from devices that are listening to and potentially recording them.

Amazon does not have a specific privacy policy for the Echo or its other devices, and that Amazon's general privacy policy does not include details on recording.

Voice-activated assistants such as the Echo and Google Home have gone mainstream. More than 60 million U.S. consumers will use a smart speaker at least once a month this year, with more than 40 million of them using Amazon's devices, according to EMarketer Inc.