EUREKA -- A minor earthquake shook parts of northwestern Montana Wednesday morning, but apparently caused no damage.

People reported pictures falling off walls, said Chrystal Stacy, a Eureka-area emergency services dispatcher. There were no injuries.

It was just so unbelievable when it happened, because it's something you don't expect up here," Stacy said.

The U.S. Geological Survey said the quake had a magnitude of 3.9 and hit at 10:24 a.m. It was centered about 12 miles west of Eureka.

Law enforcement officers said the quake was felt in Libby, Eureka and the Yaak Valley.