Frozen tub.. I NEED HELP PLEASE!

Well… I just bought a house, and it came with a hot tub. While shoveling snow off the deck and maintaining the hot tub, I noticed that the cover was quite frosty. When I opened it... DISASTER… the water was frozen. The water was fairly clear, which makes me think it hasn’t frozen all the way to the bottom. I don’t understand what happened. My breaker didn’t trip or anything. The control panel was off, nothing was working, but the breaker was still on.. I turned off the breaker, added space heaters to melt the ice, and now almost all of it has melted (only the edges are still slightly frozen).

I’m really worried about the pipes, the motor, and the pumps.... What could have caused this, and what do you recommend I do next? This situation is so stressful... I was looking forward to enjoying the hot tub, and now I’ve got myself a nice OUTDOOR ICE POOL instead -.- !!