Residents in parts of the US northeast reported hearing mysterious noises and feeling the ground shake Thursday afternoon, and officials say it was caused by multiple sonic booms.
Reports began spilling in on social media around 1:30 p.m. ET.
The Brigantine, New Jersey police department received so many calls about the tremors it issued an advisory at 2:38 p.m. asking people to stop tying up its phone lines.
“We are aware of the ongoing tremors. We have no confirmed information as to their origin. Please keep our phone lines open for emergencies.”
At first an earthquake was suspected, but the United States Geological Survey (USGS) confirmed it was in fact a sonic boom, recorded at 1:24 p.m. Thursday, the “First of multiple over the following hours.”
“At least nine sonic booms were recorded in the following hour and a half. Reported from southern New Jersey along the Eastern Seaboard to Long Island, New York,” the USGS reports.
A sonic boom is a thunder-like sound heard on the ground when an aircraft flies overhead faster than the speed of sound. The sonic booms would occur in different location as the aircraft travels, which explains the trail of reports across the region.
Some remain skeptical of the explanation.
While it was first unclear what aircraft was responsible for the sonic booms, a Navy spokeswoman says an F-35C from Naval Air Station Patuxent River, Maryland, was conducting supersonic testing off the east coast at the time.
The jet has a top speed of nearly 1,200 mph (1,931 kph).
With files from The Associated Press