HILLSBOROUGH, N.C. (WNCN) — A loud boom heard and felt in Hillsborough late Thursday morning was an earthquake, the United States Geological Survey has confirmed with CBS 17.

According to Thomas Pratt, a research geophysicist with the USGS, the magnitude 2.2 quake didn’t initially register, but further analysis showed it was an earthquake.

The USGS earthquake map shows the epicenter of the tremblor was near Arbor Lane in Hillsborough, just south of the interchange between Interstate 40 and Interstate 85.

(U.S. Geological Survey)

It’s estimated the earthquake occurred at a shallow depth of 5.4 kilometers, or 3.3 miles, but Pratt said the margin of error in that estimate is plus or minus two miles.

Pratt said that because the location of the earthquake was next to a mine, it was initially thought to be a mine blast, but further investigation showed it was not.

Small earthquakes are not uncommon — Pratt said there could be a few dozen a year in North Carolina — but don’t often register on measuring scales.

The boom was felt in several parts of Orange County, with more than a dozen reports to officials about noise, shaking and rattling buildings.

This is a developing story. Check back for updates.