HomePod mini woke me up at 2:00 AM with an Alarm

I have never, ever set an alarm on my HomePod minis. I use them to play music and to issue Siri commands. I have one in the bedroom. This morning at just before 2:00 AM the mini in the bedroom issued three loud alarm-like tones three or four times in a row and then stopped. I got up and unplugged it.

As I said I have never set an alarm on the HomePods. This sounded like some sort of warning, like a smoke alarm or something. Why would it do something like this?

I'm going to keep it off until I get an explanation and some sort of assurance that it will never happen again. I value my sleep too much. And while I haven't spoken to my neighbors, I wouldn't be surprised if they heard it as well. It was that loud.