An earthquake preliminarily measured at magnitude 6.5 struck near the center of Idaho on Tuesday, according to the U.S. Geological Survey.
The shaker happened at 5:52 p.m. about 45 miles west of Challis, Idaho, the USGS said. Its depth was a little more than 6 miles, according to the agency.
Possible damage was still being assessed. It wasn't immediately clear whether there were injuries.
About 100 miles to the west-southwest, police in Boise said they felt the temblor.
"Yep we felt it too," the department said on Twitter. "No reports of damage at this time."
The area of the quake is fairly remote. NBC Montana reported that the quake could be felt in its area.
Aftershocks measuring 4.6, 3.4 and 3.6 registered in the area Tuesday evening. Lucy Jones, a geophysicist at the California Institute of Technology, said on Twitter that residents of the region "should expect more" jolts.
She noted that a magnitude 7 earthquake struck Idaho in 1983.