A small early morning earthquake rumbled in the Black Hills on Thursday.
Sensors detected the quake in Custer State Park near the Black Hills Playhouse and Center Lake at about 2:45 a.m. The location is about eight miles south of Mount Rushmore.
Officials with the Sanford Underground Research Facility say their staff safely evacuated a few of their underground labs after the quake was felt there around 8:50 a.m. Thursday morning.
Lab personnel will inspect the lab to make sure there are "no unusual circumstances" before allowing re-entry. Lawrence County Emergency Management was also notified and is on standby at Sanford Lab.
The U.S. Geological Survey says the quake registered 3.5 on the Richter scale at a depth of four kilometers.
The USGS says it is unlikely that many felt the quake unless they were very close to the epicenter.