MADISON, Wis. -- Westbound lanes of Interstate 94 near Johnson Creek were closed indefinitely on Tuesday night and a detour has been set up because of rising water of the Rock River.

The lanes will be closed until further notice, although eastbound traffic isn't affected, WISC-TV reported.

Authorities said that the Rock River is currently just 5 inches from the highway. State officials said that they decided to close the westbound lanes as a precaution.

"At this point, there's nothing wrong with the bridge. At this point there's about 5 inches of leeway. But that water level was checked earlier today and had lots of room, and now we're 5 inches from having the water touch the girders," said Sgt. Greg Jenswold, of the Wisconsin State Patrol.

Officials said there is concern that air pockets could form under the bridge, straining its structural integrity.

A detour will take travelers off the interstate for about nine miles. Drivers will exit at Highway 26 near Johnson Creek and return at Lake Mills.

The river isn't expected to crest until Friday and more rain is in the forecast. Jefferson County Emergency Management said it expects the river to rise at least another 6 inches.

Emergency Operations Center spokesman Mike Goetzman said eastbound lanes are higher and shouldn't be affected by the closure. He said no other interstate lanes have been shut down yet due to the flooding, but a portion of I-94 near Highway 33 around Portage is being monitored.

Goetzman said that conditions at various dams threatened by high water remain about the same.

He said that police and fire personnel at Mukwonago will be monitoring the Mukwonago Dam overnight, and residents of a downstream apartment complex had been notified but not evacuated.

The Montello Granite Dam on the Montello River in Marquette County is experiencing high flows and the city of Montello is sandbagging downstream residences.

The Red Cross said that its shelters are housing four people at Columbus, three from Gays Mills and Soldiers Grove, 10 from La Farge, 16 from Reedsburg and four from Avoca.

Forecasters expect about an inch more rain throughout southeast Wisconsin starting Thursday afternoon and into the evening, but the storm front will be gone by Friday morning.