The red star marks the location of a 2.3 magnitude earthquake early Friday morning near Greenwood. U.S. Geological Survey

SOUTH PARIS — A mild earthquake rumbled through western Maine early Friday morning, according to experts.

The epicenter of the earthquake, which registered as 2.3 in magnitude by the U.S. Geological Survey, was three kilometers west of Greenwood shortly before 2:30 a.m., according to the federal agency.

Reports by people experiencing seismic activity came from residents in Greenwood, Bethel, South Paris, Norway, Bryant Pond, West Paris and Harrison, according to the agency.

Allyson Hill, director of Oxford County Emergency Management Agency, said 911 dispatchers received calls from some people who reported hearing an explosion, “which was later confirmed to just be the sound of the earthquake. The earthquake did not cause an explosion.”

Oxford County Sheriff Christopher Wainwright said dispatchers fielded roughly 20 calls from people who said they had heard a loud noise they thought might have been a train derailment or some sort of explosion that shook their houses.

Maine State Police checked with the Federal Aviation Administration to see whether the noise might be related to a sonic boom or aircraft crash, but none had been reported, he said.

Greenwood fire was dispatched to check on a suspected explosion that turned out to be unfounded, Wainwright said.

A reported structure fire in Bethel at roughly 9:30 a.m. Friday was apparently unrelated to the earthquake, Wainwright said.