With investors remaining bullish about the economy and indulging in some hectic buying at Blue Chip counters, the Sensex crossed the psychological 17,000 mark on Wednesday the early trade. The Bombay Stock Exchange benchmark Sensex shot up by nearly 104 points to 16956 with oil and gas, IT, Metals and auto sector stocks leading the rally. The wide based National Stock Exchange index Nifty moved up by 50 points to 5056 a short while ago.