WASHINGTON (AP) — Legislation supposed to make minor fixes to a 2005 highway spending bill sparked fierce debate in the Senate Wednesday over what to do about a $10 million Florida project apparently slipped into the bill after the House and Senate voted on it.

Sen. Tom Coburn, a leading critic of earmarks, or special projects promoted by lawmakers, sought creation of a House-Senate commission to look into how the "Coconut Road Interchange" project made its way into the five-year, $286 billion highway bill three years ago.

Sen. Barbara Boxer, chairman of the Environment and Public Works Committee, countered with a proposal to have the Justice Department review allegations of impropriety and possible violations of federal criminal law.

Boxer, D-Calif., said the bill, which fixes errors and makes modifications to more than 400 projects included in the 2005 act, was also being held up by "presidential politics ... dealing with the gas tax."

Sen. John McCain, R-Ariz., the presumptive GOP presidential nominee, may offer an amendment with fellow Arizona Republican Jon Kyl that would suspend the 18.4 cent-a-gallon federal gas tax between Memorial Day and Labor Day as a means of helping drivers hit by high gas prices.

On Wednesday McCain sent letters to Democratic presidential nominees Sens. Hillary Rodham Clinton, D-N.Y., and Barack Obama, D-Ill., asking them to support the gas tax holiday. The tax is the main source of revenue for the Highway Trust Fund that pays for highway and bridge construction projects.

The original highway bill, when it was approved by the House and Senate, included $10 million for improvements for I-75 in southwest Florida, one of more than 6,000 earmarks in the bill. But the version of the bill that was sent to the president for his signature redirected that money to the Coconut Rd. Interchange in Lee County.

Coburn said it's not clear how or when the change was made. But Rep. Don Young, R-Alaska, in 2005 the chairman of the House Transportation Committee, has previously said that he backed the earmark in at the request of community residents. "I think it's the right thing for the state of Florida, and you know, right now, they're supportive of it," he said in an interview this week with the Associated Press.

His press spokeswoman, Meredith Kenny, said Wednesday that Young supports an open earmark process and he has no objection to lawmakers looking into how the Florida project came about. Young has not been charged with any wrongdoing, although he has been linked to a Florida developer who held a fundraiser for Young in 2005 and stood to benefit from the earmark.

Coburn said he was against the idea of turning the matter over to the Justice Department. "I have great qualms, great worries about ceding to the Justice Department the power to investigate us."

But Boxer said the joint House-Senate panel proposed by Coburn raises constitutional issues of one part of Congress investigating the other.

Ryan Alexander of Taxpayers for Common Sense urged lawmakers Tuesday to support the Coburn proposal. "Simply put, one project was substantially altered after Congress voted and before it went to the president's desk ... It is incumbent on both the House and the Senate to get to the bottom of this deception."

Votes on the issue could come on Thursday. Earlier Wednesday the Senate defeated, 78-18, a proposed amendment by Sen. Jim DeMint, R-S.C., to eliminate all the new earmarks in the bill. That would have included $45 million for a magnetic-levitation rail project in Las Vegas.

The White House has also voiced opposition to the legislation, which passed the House a year ago, because of "strong concern that the majority of the bill is devoted to earmarks." In making modifications to existing projects, it said, the bill is "effectively creating new earmarks."

But Boxer described the legislation as "a mini-economic stimulus bill" that would release $1 billion from the Highway Trust Fund to build roads, fix bridges and run transit systems. She said it could create 50,000 jobs.

The bill is H.R. 1195.