UPDATE (9:10 p.m., June 7, 2012): The Wisconsin State Patrol has released details, including the names of the drivers involved, about Thursday's multi-vehicle crash on Interstate-94.

According to the report, a flatbed semi truck driven by Rickie R. Bolen, 55, of Kenton, OH, ran into the back of three vehicles that had slowed for traffic ahead. The driver of the first vehicle struck, Mary A. Kielpinski, 63, of Eau Claire, suffered life-threatening injuries and was taken to Regions Hospital by LifeLink helicopter.

The other two vehicles struck were driven by Sharelle M. Bowser, 24, of Hastings, MN, and Karen P. Borgeson, 55, of Detroit Lakes, MN. 

A second semi truck drove into the median to avoid the other vehicles. That truck was driven by Christopher N. Briggs, 45, of Madison Heights, MI.

Traffic was backed up for several hours and routed around the area via Highway 63 at Exit 19 to Highway 29 to River Falls and to Highway 35 into Hudson. The westbound lanes were reopened at 6:07 p.m.

The crash remains under investigation.

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UPDATE (3:18 p.m., June 7, 2012): The Wisconsin State Patrol has issued the following statement about today's crash: 

A multi vehicle crash on I-94 at milepost 9, near the WIS 65 exit has closed the westbound lanes of the interstate. Two semi trucks and three automobiles were involved in the crash shortly before noon today.

Westbound traffic is being rerouted at Exit 19 in Baldwin. Motorists will take WIS 63 south to WIS 29 west to WIS 35 north to re-enter the I-94.

Emergency personnel are on the scene and the closure is expected to last for at least two more hours.

Details of the crash are not yet known, but serious injuries have been reported and some of those injured have been airlifted to Regions Hospital in St. Paul.

Motorists should drive with extreme caution in the area and prepare for delays. 

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ORIGINAL POST: A crash on Interstate-94 at about 11:45 a.m. has westbound traffic backed up about five miles, according to Wisconsin State Patrol.

Emergency crews from St. Croix EMS, Hudson Fire Department, a LifeLink helicopter and other agencies are responding to an overturned semi truck blocking all westbound lanes of I-94 at milepost 9.

Eastbound traffic was stopped as well while the helicopter landed on the freeway. One patient was transported by helicopter.

Westbound traffic is being routed south on Highway 65 at Exit 10 all the way to Highway 35 in River Falls. Traffic is re-entering the freeway at the Exit 3 interchange. 

Originally, westbound traffic was being sent north on Highway 65 to westbound Highway 12 and re-entering the freeway at Exit 4, according to Wisconsin State Patrol.

For up-to-the-minute traffic information, check out the Hudson Patch Traffic Map.

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This post will be updated when more information is available.