The Senate voted Thursday to have the Justice Department investigate how a member of Congress changed a $10 million earmark in a 2005 highway spending bill after both houses had already voted on it.

The earmark was for a local road project in Florida, but even Florida lawmakers have said the money was not needed.

Members of both parties in the House and Senate have been in an uproar over the revelation, and scrutiny is falling on Rep. Don Young, R-Alaska. He is not charged with any wrongdoing, but has been linked to a Florida developer who stood to benefit from the earmark, which was for work on the “Coconut Road Interchange” project near Fort Myers.

“Serious allegations have been made about the motives of this member for doing this,” Senate Majority Leader Harry Reid said. “The facts are not certain but some say they're clear.”

Sen. Tom Coburn, R-Okla., who initially proposed creating an eight-member bicameral body to probe the matter, said plainly that Congress was in the dark about the earmark.

“A bill agreed to by both houses of Congress was changed before it got to the president without our knowledge,” Coburn said.

Coburn’s proposal was rejected, but the Senate voted 63-29 to get the Justice Department involved, a plan proposed by Sen. Barbara Boxer, D-Calif.

"I'm so angry about this. I'm so upset about this. I'm sick about this,” she said. “I think it’s very possible people ought to go to jail here. A Senate and House committee can’t send anybody to jail, they simply can’t.”

Both houses approved the highway bill back in 2005 with about 6,000 earmarks, including one to widen I-75 near Coconut Grove, Fla. But after the bill was passed by both houses, somebody changed $10 million dedicated to the I-75 widening to $10 million for an interchange, which would install off-ramps, greatly improving the value of nearby land.

Coburn said it’s not clear who is responsible.

“Nobody knows exactly where this ... change happened,” he said. “Some may think they do but we don’t know that.”

But it was committee staffers working for Young who directed the money for the interchange during what they say was a process of making technical corrections to the legislation.

Young was at the time a key member of the Transportation Committee who went to Florida to listen to locals plead for money to widen I-75.

However, Young flew down to Florida on a private plane owned by developer Daniel Aronoff, who later helped raise $40,000 for Young, a congressman from faraway Alaska. Aronoff owns thousands of acres along Coconut Road.

Young’s office welcomed the investigation.

"Congressman Young has always supported and welcomed an open earmark process. If Congress decides to take up the matter of this particular project, there will be no objection from Mr. Young," spokeswoman Amanda Kenny said in a written statement.

Young was a sponsor on the I-75 earmark and had previously sponsored another earmark for Coconut Road that died.

It is not clear how much Young knew about his committee staffers’ tweaking of the bill, or who was behind the move.

There were some objections Thursday to the decision to invite the Justice Department into the process.

Coburn strenuously objected, saying Congress should learn the facts first with its own bipartisan investigation.

“We have just voted an invitation for the Justice Department to investigate a rules violation in either the House or the Senate,” he said. “We have set an amazing precedent.”

House Minority Whip Roy Blunt said he didn’t know if the Justice Department was the right entity to investigate, but “there are clearly problems in the mechanics of what happens with legislation here, and we ought to find ... what they are.”

Speaker Nancy Pelosi doesn’t want the Justice Department on the case either, preferring instead to have the House Ethics Committee investigate.

FOX News’ Jim Angle and Trish Turner and The Associated Press contributed to this report.