The collapse in shares of subprime mortgage companies over the past month rewarded so-called short sellers who bet that rising defaults among the riskiest borrowers would curb lenders’ profits.

Some traders who predicted declines in shares of New Century Financial Corp., NovaStar Financial Inc. and Accredited Home Lenders Holding Co. say such stocks may fall further as loan delinquencies increase and demand for mortgage-backed securities wanes. New Century sank 90% last month, while NovaStar lost 73%. Accredited slid 54%.

“The subprime guys are history,” Steven Persky, chief executive officer of the $1.1 billion Los Angeles-based hedge fund Dalton Investments LLC, said. Dalton began shorting shares of subprime lenders two years ago. “They’re ultimately going to have to file” for bankruptcy.

New Century, NovaStar and Accredited Home were some of the most-shorted American stocks from February 12 to March 12, the date of last month’s short-sale statistics from the New York Stock Exchange.

Short interest in the stocks climbed last month after New Century, the biggest specialist in home loans made to people with relatively low credit ratings, and HSBC Holdings Plc, Europe’s biggest bank, said losses from bad American home loans were piling up faster than they expected.

About 36% of New Century’s shares available for trading, or float, was borrowed and sold to profit from falling prices. Traders sold short 46% of Accredited’s float, while 44% of NovaStar’s float was shorted.

A NovaStar spokesman, Jeff Gentle, declined to comment. A New Century spokeswoman, Laura Oberhelman, didn’t return a voice message seeking comment. Accredited spokesman Rick Howe also didn’t reply to a message seeking comment.

Defaults on subprime loans increased as competition and a slower housing market prompted lenders to lower their standards and give mortgages to borrowers who couldn’t make their monthly payments.