MIDDLESEX, Vt. (AP) – A 120-foot portion of a bridge being replaced fell unexpectedly into the Winooski River after the construction barges it was sitting on were swept away by high water, authorities said Tuesday.

Half of the Route 2 bridge between Middlesex and Waterbury had been disconnected from the abutment and the concrete pier and was floating on barges tethered by steel cables – in preparation for its removal – when heavy rains caused the water to rise Sunday night.

The high water washed the four barges out from underneath the bridge, causing it to tip over and fall into the river, said Vermont Agency of Transportation spokesman John Zicconi. “The water just came up a little heavier and faster than anyone had anticipated,” he said.

“Fortunately, no one’s hurt, no one was here, by my understanding, no report of injuries. So what we now have is a bit of a cleanup to do,” he said at the scene.

CCS Constructors of Morrisville, which planned to cut up the bridge and remove it by crane from the water, doesn’t expect the mishap to delay the project.

but said heavy rains forecast in the coming days could hamper work this week.

“We don’t anticipate we’ll have a problem making that Aug. 1 deadline,” said Chris Chauvin, general manager.

The first half of the bridge had already been removed when the accident happened. Workers planned to cut up portions of the second half of the bridge as it sat on the barges, and remove it by crane.

“It creates an engineering problem now for us. We’ve got to figure out now how we can cut the bridge up into sections that needs to get cut up and lift it out of the river,” Zicconi said.

The state Agency of Natural Resources is keeping an eye on the bridge, but doesn’t have any major concerns since it’s an open truss, allowing debris to wash through, said spokeswoman Sabina Haskell.

That portion of the river had already been off limits to kayakers, swimmers and anglers because of the construction.

The bridge has been closed to traffic since late May after engineers determined there were structural concerns with the 80-year-old span.

The state plans to replace it with a temporary bridge by Labor Day, with construction of a new bridge to begin in 2010 with a likely opening in 2011.

It’s unclear why the barges broke free from the steel cables holding them in place, Zicconi said.