Minnesota transportation officials are concerned underground tunnels could undermine U.S. Highway 169 near Chisholm in the Iron Range.
Miners pursuing iron ore dug the tunnels decades ago.
A hole that opened in the highway's median in 2007 drew attention to the problem. Now, a team from the Minnesota Department of Transportation is looking at what can be done to prevent a wholesale collapse.
Assistant district engineer Duane Hill says the team has gathered a lot of information and is working on a plan to mitigate the danger. They hope to have it ready this spring.
The team is most concerned about tunnels running beneath one 1-mile stretch of highway on the southern edge of Chisholm and another 1-mile section just west of town.
(Copyright 2009 by The Associated Press. All Rights Reserved.)
