WASHINGTON (AP) -- Internet users skeptical of junk E-mails promising easy money, miracle cures, and dream dates are right to be wary: The government says two-thirds of the spam messages clogging online mailboxes probably are false in some way.

The Federal Trade Commission said Tuesday that spam E-mails involving investment and business opportunities are especially dubious, with an estimated 96 percent containing information that probably is false or misleading.

The FTC studied a random sample of 1,000 unsolicited E-mails taken from a pool of more than 11 million pieces of spam it has collected. The agency looked for deceptive claims in a message's text or the "from" or "subject" lines.

"In one way or another, a great deal of it appears to contain important information that is false or deceptive," said Eileen Harrington, the FTC's director of marketing practices.

As with telemarketing and other types of advertising, false claims and fraud are at the fringes of the business, Harrington said, but with spam, "there is far more deception in this medium than there is in others."

Twenty percent of the spam studied involved business opportunities such as work-at-home and franchise offers. Offers for pornography or dating services accounted for another 18 percent. Spam involving pitches for credit cards, mortgages and insurance was the third largest category at 17 percent.

Junk E-mails are a rapidly growing problem, with the anti-spam company Brightmail recording 6.7 million instances of multiple unsolicited messages being sent out in March, a 78 percent increase from a year ago.

Companies have been developing mail filters and users have been limiting distribution of their E-mail addresses to cut down on junk mail. Persistent spammers have found ways to dodge those obstacles.

The FTC plans a three-day forum beginning Wednesday to discuss how the government and businesses should deal with spam.

The FTC study found that a third of spam E-mails contained false information in the "from" line that obscured the true identity of the sender. Nearly half of that misleading information involved attempts to claim a personal relationship with the person receiving the E-mail.

Spammers also use misleading subject lines to get their pitches read, the FTC said. Many messages claim to be personal or business correspondence by using subject lines like "your order's status."

A third of the spam with false subject lines uses misleading topics unrelated to the content of the message.

Earlier this month, the FTC took a pornographic spam operation to court to shut it down after receiving 46,000 complaints about that kind of deception. The FTC said the spam used deceptively innocent subject lines like "I found your address" or "wanna hear a joke," but when opened the E-mails displayed graphic pornographic pictures.

Several states require spam E-mail to have a subject line beginning with "ADV" to identify it as advertising. The FTC found that less than 2 percent of spam used this label.