Thick white smoke - stopped accelerating - cranking, not starting - no motor oil

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My 2001 Saab 9-5 Sedan (2.3L 4cyl Turbo 5M) recently took an uncommon road trip (80 miles). After making a quick pit stop, we restarted the car and the tailpipe began emitting a white smoke, which gradually thickened. About 5 minutes later, the smoke was incredibly dense and the car stopped accelerating. The engine wasn't overheating. We turned the car off and had it towed to a Ken Towery. The mechanic checked it out and quickly advised that the issue was likely onset by a broken part "catching" when the engine turned over and that we replace the motor. We then had the car towed back to our hometown... Since then, I've tried to start it... the engine cranks, but it doesn't start. And, I've checked the motor oil... there doesn't appear to be any. I had the car inspected on 8/18. Everything checked out OK, except for a loose oil cap (which they tightened). I had the oil changed on 6/16. Any help diagnosing this issue would be greatly appreciated!