Explosions without explanation have erupted in a rural region about an hour north of Philadelphia more than 20 times in the last two months, and federal experts have now joined in the effort to solve the ear-popping mystery.
The loud booms have awakened residents in the northern section of Bucks County, Pennsylvania, but state police have been unable to determine the cause of the sounds. The first blast was reported April 2 in the Quakertown area.
State police did not say what they think may be the origin of the unusual disturbances, which have led to numerous conspiracy theories among the locals: from alien landings and meteor strikes to stolen military munitions.
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Each of the incidents over the last two months have occurred between the hours of 1 and 3:30 a.m., state police said May 30 in the first statement on their investigation.
A police spokesman said he could not provide more details about the exact dates and locations of each blast.
An agent with the federal Bureau of Alcohol, Tobacco and Firearms confirmed that the ATF is now involved in the investigation. She said the bureau is aiding the state police and local police departments, including Springfield, Nockamixon and Richlandtown.