Lancaster, Pennsylvania
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The booms are loud and deep, enough to rattle the dishes.

"I have heard it four times Saturday night through Sunday night," says Carolyn Risko, who lives south of Lancaster. "It's very loud and shakes the house."

She and other residents of the area have been trying to determine the cause of the loud noises, but they haven't had any luck.

Risko says she went outside after each boom but "didn't see anything."

Residents contacted Manor Township police and spoke to an officer who also heard the booms, Risko says. Firefighters, too, patroled the area searching for the cause.

"They can't pinpoint a location so they can't really investigate it," Risko says.

Manor Township police Sgt. Gary Gardner says he doesn't think anyone has tracked down the source of the booms.

"I don't know that anything was substantially found on that," he said Thursday. "It could have been fireworks, or someone throwing quarter sticks of dynamite."

There have been no reports since last weekend, he noted.

Melanie Sturgis, who lives in the Georgetown Hills development off Route 741 and Charlestown Road, led a discussion on Facebook among residents who also heard the noises.

She described the noises as "four loud explosion-type sounds." "They were not fireworks," she said. "They were loud and shook some houses."

She said people reported hearing them in Millersville, Mountville and surrounding areas.

The first boom was around 10:30 p.m. on Saturday, Sturgis said. Three followed on Sunday, but earlier in the day, she said.

She shared a lengthy conversation among numerous residents of the area who also were concerned about the noises.

Charles Scharnberger, a retired geology professor at Millersville University, said seismic readings show there was no earthquake activity in the region over the weekend.

Lancaster Airport director David Eberly said he sometimes can hear sonic booms and explosions from military maneuvers at Fort Indiantown Gap "if the wind is right," but he said he knows of nothing in the air over the weekend that could have caused the sounds.

"In any case," he said, "I can't believe the military would be doing maneuvers that break the sound barrier over land."