Is this a problem with my washing machine, or should I look for another cause?

Yesterday I went down to our unfinished basement to start a load of laundry. There was a huge puddle on the floor, but no obvious sign of where the water had come from. I thought it might have seeped into the basement from melting snow, but then I noticed two or three inches of water in the washing machine. The machine hadn’t been turned on in a couple of days, and I know the water wasn’t there when I last removed wet clothes from it.

So, can a washing machine partially fill with water and leak when it isn’t turned on or running? Sometimes it does leak a bit when I run it. Or, should I be looking for another source?

Just to add to the confusion, I did a couple of loads of laundry yesterday with no further leakage.