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BELLEFONTE, Pa. (AP/CBS) — Officials in a central Pennsylvania borough are investigating after receiving reports of loud blasts and tremors in the area.

Officials Warn Upper Bucks County Residents Some Unexploded Devices Could Still Be Live Following Mysterious Blasts

Bellefonte borough Assistant Manager Don Holderman tells the Centre Daily Times his office began receiving calls at about 11:45 a.m. Thursday from people who reported tremors that feel like an earthquake and hearing loud blasts.

The Bellefonte Area School District says in a tweet that schools in the district have experienced “tremors and loud noises” but classes remained in session.

“We are safe and are continuing our school day as normal,” school officials added.

The U.S. Geological Survey says there was spike on a seismometer but there wasn’t enough data to get a good location of the event or to determine exactly what caused it.

The state’s seismic network showed activity on the maps as well.

Small Earthquakes Rattle Reading Area

Geophysicist Paul Caruso says the equipment can also register things like explosions from quarries or mines or mine collapses.

Two months ago, about 137 miles northeast of Bellefonte, Reading reported small earthquakes that shook the area.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)