For the better part of the past month, and as recent as this past weekend, residents in towns across upper Bucks County have been springing out of their beds to the sound of deafening explosions.

The blasts seem to occur in quick bursts in the middle of the night. One Quakertown resident told FOX29 last month that she heard the "boom" several times in April, generally some time between two and six in the morning.

Another man in Nockamixon Township told the Bucks County Herald that an apparent explosion left a four-foot wide cavity in the ground.

Complaints from residents in Richland Township prompted police there to issue a statement on Facebook in mid-April. Authorities said the explosions appeared to be concentrated in an area near the border of Richland and Milford townships.

In the weeks since these initial reports, the investigation has been taken over by Pennsylvania State Police, but the mystery remains unsolved.

"There were some more explosions over the weekend," Richland Township Police Chief Richard J. Ficco said Tuesday morning. "For a while, I was logging them myself, but now that it's been pushed out of our jurisdiction, it's kind of difficult to take further steps with it."

Ficco said he hasn't personally heard the explosions — he was taking reports from residents — but one of his officers caught one.

"He said it was a very loud boom," Ficco explained. "It's not fireworks. It's not firearms. He couldn't really describe it, but it sounds like a very, very loud boom."

One of the first reported explosions seems to have originated near Lonely Cottage Road in Nockamixon Township, according to the Bucks County Herald. That boom was reportedly heard as far north as Riegelsville and as far south as Point Pleasant.

The area last experienced a notable earthquake in 2003 centered in nearby Milford, N.J., which was accompanied by a thunderous boom heard in Bucks County according to one media report, but the United States Geological Survey hasn't recorded any seismic activity in upper Bucks County since well before the overnight explosions began.

Residents in Facebook groups have thrown out various theories — underground blasts, meteors, meth labs and sonic booms. None of them would seem to explain the repetitive nature of the explosions in and around the Quakertown area.

Ficco said his department continues to search for answers and participate where needed in the State Police investigation.

A call to the Pennsylvania State Police Dublin Barracks on Tuesday morning for an update on the investigation was not immediately returned.

"I've heard from other people through different avenues close to this that when the explosions go off, houses are shaking," Ficco said. "That's kind of upsetting, I would imagine."