From the mid-20's, there didn't have to be any "reason" for the jump - just a few buyer's finally figuring out how undervalued it was and still is. If 2006 earnings are where I think they'll be, we should have at least another $10-$15 upside from today's price in the next 6 months. Even much higher if the Ruble continues to appreciate against the dollar - at last check I believe close to 40% of MTL's income was in local currency which makes MTL even better as the Dollar will most likely weaken further over the next several years.
Actually, the volume has been up for the last 7 or 8 trading days. This is from technical point - a very bullish sign. Considering that there is no news, I would believe that large institutions are buying.