Thomas MacMillan/New Haven Independent

Residents of New Haven, Conn., got an eerie Halloween surprise when a famed tree uprooted during Hurricane Sandy, unearthing the bones of a woman who died nearly 200 years ago - and maybe from others who died during the same period.

Around 6 p.m. on Monday the famous tree at New Haven's Upper Green, named the "Lincoln Oak" after President Abraham Lincoln, was uprooted as Sandy swept through. New Haven resident Katie Carbo was passing by when she saw the back of a skull in the 60- to 70-foot-tall tree's roots, police said.

Carbo quickly contacted the New Haven police, and soon after detectives were on the scene as a crowd of onlookers formed. Officer David Hartman with the New Haven Police Department told ABCNews.com that the timing of the discovery was particularly striking.

"I found myself standing there, among onlookers saying, 'Wow this is really cool, the day before Halloween,'" he said.

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Detectives from the NHPD's Bureau of Identification and the state Medical Examiner's office came to collect the bones, which Hartman said included a spine and rib cage.

New Haven police also contacted staff from Yale University's anthropology department, Hartman said, and the New Haven Independent shot some images.

The NHPD said that it had not launched a criminal investigation into the discovery, and that the remains were being taken to the medical examiner's office.

"What we haven't yet determined is what will happen with the remains," Hartman said. "This archaeological event that is going on will last for probably about a week, they're estimating."

New Haven police said that the bones belonged to a probable victim of yellow fever or smallpox, who likely was buried between 1799 and 1821, when the headstones were removed to New Haven's Grove Street Cemetery, but the bodies were never relocated.

Later, the New Haven Independent, citing an initial investigation by an anthropologist and a state investigator, reported bones at the scene actually may be from two or more centuries-old skeletons - not just one.

The Lincoln Oak was planted at the town green by Admiral Andrew Hall Foote's Grand Army of the Republic post, in honor of the 100th anniversary of Lincoln's birthday in 1909, according to the New Haven police.

Robert S. Greenberg, a local historian, said that the town green is the burial ground for as many as 5,000 to 10,000 bodies.

Hartman said that he learned today that this is actually not the first time this has happened on the historic Upper Green. According to a local historian, the same situation occurred in 1931, when an uprooted tree brought up skeletal remains, he said.

New Haven is not the only place where the dead were unearthed in Sandy's wake. The Associated Press reported that at a cemetery in Crisfield, Md., two caskets were forced out of their graves, making their sides visible from the grass, after the cement slabs covering the graves became dislodged.

Alex Brandon/AP Photo

The corpses remained inside the caskets.