Sensex plunged nearly 600 points in about 50 minutes on Tuesday to hit the day's low of 76,501.52 at around 12:25 pm. Weaker Asian peers, like South Korea's KOSPI and Japan's Nikkei 225 indices, were among the reasons behind Sensex's fall. Persistent FII selling and a decline in the Indian rupee's value against the US dollar were also reasons.