Shares of Bermuda insurance giant XL Capital Ltd. may have been sold short by terrorists raising money for the attacks this month on Washington and New York, according to information released by the New York Stock Exchange to Reuters.

The Reuters story said the short interest trends in 24 top US airline, insurance and investment bank stocks were decidedly mixed in the three months before the September 11 attacks that some have linked to possibly suspicious trading activity.

Hard-to-explain increases in short interest were evident in only a handful of the stocks based on the NYSE data, which analysts and traders said was difficult to interpret.

Regulators worldwide are investigating whether those behind the attacks that left thousands dead tried to profit from their inside knowledge by playing the markets.

Some attention has focused on short selling of stocks hit hard by the attacks.

Selling short is a process where investors borrow shares from a broker, order them sold and then pocket the money. Investors wait for the price to drop.

If it does, one buys the shares at the lower price and turn them back over to a broker (plus interest and commission) and pocket the difference.

The NYSE data showed significantly and steadily increased short interest in just five of 24 leading airline, investment bank and insurance stocks from June 15 to September 13.

The data shows XL Capital saw short sales of its stock jump sharply on the NYSE to about 5.1 million shares in September from 1.8 million in August.

XL Capital also saw short sales of 1.7 million in July and 1.6 million in June.

Others include UAL Corp., parent of one of the airlines whose jets were hijacked and crashed.

United Airlines had short interest of about 4.4 million shares in September, well above August's level of 3.1 million, July's of 2.6 million and June's of 2.4 million.

Short sales of stock in Morgan Stanley , the investment bank, crept up steadily to 17.6 million shares in September from 15.8 million a month earlier, 14.9 million in July and 14.5 million in June.

Lehman Brothers, an investment bank that had two floors in the World Trade Center, had about 7.0 million shares sold short by mid-September, compared with roughly 5.6 million in August and July and 4.3 million in June.

CNA Financial, a leading business insurer that reported an unexpectedly large loss August 2, saw its short interest rise more than five-fold in September to 1.8 million shares from a range of 345,000 to 386,000 shares since June.

"It's very difficult to conclude just from looking at the raw data whether there's any evidence or not," of suspicious trading, said Ed Keon, chief quantitative strategist at Prudential Securities. "It's certainly conceivable. Whether it actually happened or not, I'll leave it to people with much more experience in this area than I have."

Shorting is a common, but risky way to exploit a falling share price.

Experts on Mid Eastern extremists said Osama bin Laden or associates may be capable of sophisticated financial speculation. But some doubted whether bin Laden, estimated to be worth $300 million but is holed up in infrastructure less Afghanistan, could have shorted NYSE stocks.

Like UAL, shares in investment banks Morgan Stanley and Lehman and in insurers XL and CNA have also fallen since the attacks, although CNA's was already down well beforehand.