Divya Delhi : The National Stock Exchange (NSE) warned Jane Street in February that its trades appear "fraudulent and manipulative", causing it to almost suspend trading for 2-3 weeks, according to a regulatory source.Importantly, stock derivatives volume did not decrease. With Jane Street prohibited, many in the market have worried about F&O volumes.In the five days between February 1-6, NSE reported 9.8 crore index options contracts traded daily.Jane Street was out of the arena from February 7-13, yet the average number rose to 12.01 crore contracts. Between February 14-20, the number dropped to 10.2 crore contracts but was still greater than the first week.Index options sold daily averaged 9.3 crore in the last week of February, between 21st and 28th.