WASHINGTON (AP) — Federal regulators suspended trading in 35 companies yesterday in a crackdown on spam e-mail sent by unknown market manipulators who profit from a rise in the share price of thinly traded companies.The Securities and Exchange Commission said it took the action to protect investors from fraud, because the accuracy of information in e-mails about the “spammed” companies was questionable.

E-mails with messages such as “Ready to Explode,” “Ride the Bull” and “Fast Money” clog people’s inboxes — an estimated 100 million of them a week — and spark dramatic spikes in trading and stock prices before the spamming stops and investors lose their money, the SEC said.

The suspensions are part of an SEC effort called “Operation Spamalot,” and will remain in effect through March 21.

The companies’ shares are not traded on stock exchanges. They are listed on the so-called Pink Sheets, an electronic quotation service in which brokers posting quotations to buy or sell stocks are not required to investigate the background of the companies. The use of spam e-mail to hype stocks is a variation on the classic “pump and dump” stock scheme, in which the perpetrators get people to buy stocks to inflate their prices and then sell their blocks of shares at a profit. Ordinary investors can suffer heavy losses when prices tank.

“When spam clogs our mailboxes, it’s annoying. When it rips off investors, it’s illegal and destructive,” SEC Chairman Christopher Cox said at a news conference. “Today’s trading suspensions, and actions that will follow, should send a clear message to spammers: the SEC will hold you accountable.”

SEC officials said the investigation continues and they are seeking to identify people behind the schemes.

“We are ... committed to tracking down those who prey on investors with false or misleading information,” said Linda Thomsen, the agency’s enforcement director.

In one case cited by the SEC, shares of Apparel Manufacturing Associates Inc. closed at 6 cents, on trading volume of 3,500 shares on Friday, December 15. After a weekend spam campaign, trading on the following Monday reached 484,568 shares and the stock climbed to over 19 cents a share. Two days later, on December 20, it hit 45 cents a share. By December 27, Apparel Manufacturing stock was down to 10 cents on volume of 65,350.

In addition to Apparel Manufacturing, the companies are: Advanced Powerline Technologies Inc., America Asia Petroleum Corp., Amerossi International Group Inc., Asgard Holdings Inc., Biogenerics Ltd., China Gold Corp., CTR Investments & Consulting Inc., DC Brands International Inc., Equal Trading Inc., Equitable Mining Corp., Espion International Inc., Goldmark Industries Inc., GroFeed Inc., Healtheuniverse Inc., Interlink Global Corp., Investigative Services Agencies Inc., iPackets International Inc., Koko Petroleum Inc., Leatt Corp., LOM Logistics Inc., Modern Energy Corp., National Healthcare Logistics Inc., Presidents Financial Corp., Red Truck Entertainment Inc., Relay Capital Corp., Rodedawg International Industries Inc., Rouchon Industries Inc., Software Effective Solutions Corp., Solucorp Industries Ltd., Sports-stuff.com Inc., UBA Technology Inc., Wataire Industries Inc., WayPoint Biomedical Holdings Inc. and Wineco Productions Inc.