A large ice chunk, which is believed to have fallen out of the sky, is sparking quite the mystery in Alliston.

Kate Bearse was headed for a soak in her hot tub on Saturday afternoon when she heard a loud thud come from beside her home.

"I had just stepped out the door. I had my towel, my phone to plug it into the hot tub and walking along here I heard this loud crash," she says.

She found a giant chunk of ice about 45 centimetres long. Kate’s husband George Bearse estimates the chunk weighed about 2.7 kilograms or six pounds.

The Bearses decided to keep the ice in his freezer until the mystery could be solved.

"You think you need to save this just in case you need evidence for something," George said.  

Environment Canada’s senior meteorologist David Phillips says the ice chunk could be a megacryometeor.

They're very rare, but they're always mystifying. There was nothing atmospheric that could have caused this," he says.

Another possibility is that its debris from an airplane. Transport Canada says it's aware of the incident, and is investigating.

The family says they're just happy no one was injured.

"How lucky are we that it fell directly between two houses and not on the sidewalk where the kids were out playing," says Kate.

The family plans to keep the ice in their freezer for a few more days.

They hope experts come forward, offering to study it and what might be inside.