The stock market regulator is also looking into the angle of fraud perpetrated by these entities - Altgraaf, Tap Invest and Stable Investments. Altgraaf is seen to have facilitated the sale of over Rs 4,400 crore NCDs for 75 companies and Tap Invest Rs 400 crore for over 100 companies as of November 18. Sebi is probing the exact amount raised through Stable Investments.