Update 8:30 a.m.
The department reports the semi has been cleared and both lanes are reopened.
The Montana Department of Transportation reports a jack-knifed semi has blocked both westbound lanes of Interstate 90 west of Reed Point.
The incident was reported at about 7:30 a.m. six miles west of Reed Point at mile marker 398 near the Yellowstone River Bridge.
Roads in the area are icy, the department said in a press release. Motorists can expect a detour in the area.
Check back for updates.