Volvo s70 rear wheels locked

Hi All,
I have a '99 S70 (Front wheel drive) Volvo. I went to drive it and the rear tires are locked into place and do not turn! Any ideas of what the problem could be? Thanks!

Was the parking brake on, especially for a long time?

How do you know the rear tires are locked in place? How have you tried to turn them?

No, the parking brake was not on. Yes, we tried turning them, took the tire off, etc. No go! Any idea? Thx.