The disappearance of a 64-year-old Pennsylvania woman is being investigated by state authorities, who said on Tuesday they fear she may have fallen into a sinkhole.

What Happened?

Elizabeth Pollard went missing on Monday evening after heading out to find her missing cat, Pepper, in the village of Marguerite, located about 40 miles east of Pittsburgh. The family of Pollard then called police at about 1 a.m. local time on Tuesday to say she had not been seen going out.

Pennsylvania State Police soon discovered her vehicle parked near Union Restaurant with her 5-year-old granddaughter inside, unharmed but alone.

According to trooper Steve Limani, Pollard lives in a small neighborhood across the street from where her car and granddaughter were located.

However, a sinkhole had recently opened up as emergency crews worked through the frigid night, using advanced equipment to probe the manhole-sized sinkhole.

A pole camera outfitted with a sensitive listening device revealed no signs of life, though a second inspection hinted at the presence of what may be a shoe about 30 feet below the surface.

Authorities suspect the sinkhole, likely caused by subsidence from historic coal mining in the region, opened suddenly beneath Pollard as the opening had not been seen by hunters and restaurant workers who were in the area in the hours before Pollard’s disappearance.

“It almost feels like it opened up with her standing on top of it,” Limani said.

Rescue efforts have since been intensified, with heavy machinery brought in to excavate the area.

“We’re pretty confident we are in the right place,” John Bacha, chief of the Pleasant Valley Volunteer Fire Company told Triblive. “We’re hoping there is still a void she could be in.”

How Did the Sinkhole Appear?

The sinkhole is believed to be linked to the long-abandoned Marguerite Mine, which operated until 1952 by the H.C. Frick Coke Company, according to the state’s Department of Environmental Protection. The Pittsburgh coal seam is about 20 feet below the surface in that area.

Police said sinkholes are not uncommon because of subsidence from coal mining activity in the area.

However, this incident highlights the lingering dangers of Pennsylvania’s coal mining legacy, with the state’s Department of Environmental Protection on-site to assess the area.

After the search concludes, experts from the Bureau of Abandoned Mine Reclamation will determine if mine subsidence definitively caused the sinkhole, Department of Environmental Protection spokesperson Neil Shader said.

This article includes reporting from The Associated Press.