PORTLAND (AP) - Oregon is one of the few states that places no limit on how much individuals or groups can contribute to campaigns. In exchange for that freedom, the state requires disclosure - so voters know who is providing the cash.

But Oregon treats initiative campaigns differently while they are collecting signatures than after they make the ballot. Because of that loophole, at least two groups seeking to put measures before voters in November - to allow a casino in Multnomah County and to limit state spending growth - have been able to keep their donors a mystery, The Oregonian reported in its Sunday editions.

Campaigns promoting ballot measures have until July 7 to gather more than 75,000 signatures needed to make the fall ballot. Though it wouldn't seem like an expensive process, it can cost hundreds of thousands of dollars because of legal issues and the price of hiring people to gather signatures.

Initiative campaigns must report the money they receive, but if donors give through an intermediary group, that group can keep names confidential. Another loophole exists for out-of-state groups. Unless such a group directs at least two-thirds of its nationwide political contributions into Oregon, it doesn't have to disclose its donors.

The newspaper examined thousands of pages of campaign reports in an attempt to find out who is funding the initiatives. It focused on 10 measures that have drawn the most money and found that wealthy Oregon entrepreneurs and lumber executives are the main contributors to half the measures.

Moreover, eight of the 10 measures are funded primarily by a single individual, corporation or union. Only one names at least 10 individual donors - the drive to replace party primaries with open primaries.

But the newspaper could not identify donors for the potential state spending cap, which is proposed by the Taxpayer Association of Oregon, and the casino measure.

Most of the $350,000 spent by April to get the casino proposal on the ballot was contributed by a business called Mariposa. Unless the measure makes the ballot, the company does not have to say who is fronting it money.

Bruce Studer, who heads Mariposa, told the newspaper that he will announce the casino's financial backers in August if the measure makes the ballot. State law would not require disclosure until October.

The initiative for the state spending cap raised more than $230,000 by May. More than 90 percent of the money came from Americans for Limited Government, based in Chicago, and Americans for Tax Reform, in Washington, D.C. Neither group will disclose its donors.

Secretary of State Bill Bradbury said he may ask the 2007 Legislature to close the initiative loopholes.

“I think it's just basic common sense that people should be able to have financial information about a measure that they are being asked to sign,” he said.