Share prices of some recent listings, including the scam-tainted Atlanta Ltd and Nissan Copper, have been falling over the last couple of sessions on fears of further action from the Securities and Exchange Board of India (Sebi).

It is believed that some big operators are squaring off their positions, which is accentuating the free-fall.

"It seems Sebi's action has resulted in market players anticipating similar move in scrips where prices have gone up real fast," said V K Sharma of Anagram Stock Broking.

Atlanta, which was trading at Rs 1,110 levels last week, hit the 10 per cent downward circuit, the maximum fall permitted in a given day, on Friday and Monday.

On Monday, the scrip fell Rs 100 to Rs 875.45, while Nissan Copper, which hit a peak of Rs 154.55 on January 2, has been on a tailspin ever since Sebi unearthed price manipulation in the counter. On Monday, the share hit the lower circuit to close at Rs 32.35.

The downward circuit is triggered when there are only sellers and no buyers. This also means investors cannot get an easy exit. In some counters, the circuit limit (maximum permitted movement in a counter -- upward or downward) is 10 per cent, while in others it is 5 per cent. XL Telecom, which got listed last year, was another big loser - shedding 4.87 per cent to Rs 125.20.

Shree Ashtavinayak Cinevision, another recent listing, was locked at the downward circuit of 5 per cent at Rs 217.45. Pochiraju Industries also lost 7.08 per cent on Monday to close at Rs 34.75.

On February 6, Shree Astavinayak Cinevision was quoting at Rs 383.80 and in 14 sessions lost about 44 per cent  (Rs 166.35).

"There have been some scrips, which gained irrespective of their worth on heavy exposures by operators. There is a suspicion that further action could be initiated in these scrips," a Bombay Stock Exchange broker said.

Prithvi Haldea of Prime Database, which tracks IPOs, feels that most issues are under-priced following their qualified institutional placement and it is up to the market to decide whether the stock is attractive.

"There is no law or proven mechanism to decide the valuation and justify it. If some stock gains more on first day, it is market sentiment that has made it attractive. But it is wrong to generalise that prices are touching the sky because of post-IPO manipulation," he said.

Atlanta had registered a whopping 681 per cent rise to Rs 1,446 within 55 trading days, after it got listed at Rs 150 in September 2006. The markets regulator asked the exchanges to conduct preliminary investigation into the matter, which showed that the promoters were buying heavily into the scrip.

In case of Nissan Copper, Sebi asked the exchanges to freeze payouts and transfer the stock to the trade-to-trade segment. The scrip had gained nearly 300 per cent within few days of listing amid unusually huge volumes.