The search for a woman who is believed to have fallen into a sinkhole in western Pennsylvania is moving into a recovery effort after two days of searching produced no signs of life, authorities said Wednesday.

Pennsylvania State Police spokesperson Trooper Steve Limani said during a news conference that authorities no longer believe they will find 64-year-old Elizabeth Pollard alive, but that the search for her remains continues.

"We've had no signs of any form of life or anything," Limani said.

Emergency crews and others have been trying to locate Pollard, 64, for two days. 

Her relatives reported her missing early Tuesday, and her vehicle with her unharmed five-year-old granddaughter inside was found about two hours later, near what is believed to be a freshly opened sinkhole above the long closed, crumbling mine.

Authorities said in a noon update that the roof of the mine has collapsed in several places and is so unstable that it is not safe enough to send people underground. The sinkhole is in the village of Marguerite, about 65 kilometres east of Pittsburgh.

"We did get, you know, where we wanted, where we thought that she was at. We've been to that spot," said Pleasant Unity Fire Chief John Bacha, the incident's operations officer.

"What happened at that point, I don't know, maybe the slurry of mud pushed her one direction. There were several different seams of that mine, shafts that all came together where this happened at."

'The process is long, is tedious'

Searchers were using electronic devices and cameras as surface digging continued with the use of heavy equipment, Bacha said. Search dogs may also be used.

Sinkholes occur in the area because of subsidence from coal mining activity. Rescuers had been using water to break down and remove clay and dirt from the mine, which has been closed since the 1950s, but that increased the risk "for potential other mine subsidence to take place," Pennsylvania State Police spokesperson Trooper Steve Limani said.

Crews lowered a pole camera with a sensitive listening device into the hole, but it detected nothing. Another camera lowered into the hole showed what could be a shoe about nine metres below the surface, Limani said. Searchers have also deployed drones and thermal imaging equipment, to no avail.

Marguerite Fire Chief Scot Graham, the incident commander, said access to the immediate area surrounding the hole was being tightly controlled and monitored, with rescuers attached by harness.

"We cannot judge as to what's going on underneath us. Again, you had a small hole on top, but as soon as you stuck a camera down through to look, you had this big void," Graham said. "And it was all different depths. The process is long, is tedious. We have to make sure that we are keeping safety in the forefront as well as the rescue effort."

Bacha said they were "hoping that there's a void that she could still be in."

Went missing Monday evening

Pollard's family called police on Tuesday at about 1 a.m. to say she had not been seen since going out Monday evening to search for Pepper, her cat. The temperature dropped well below freezing that night.

Her son, Axel Hayes, said Pollard was a happy woman who liked going out to have fun. She and her husband adopted Hayes and his twin brother when they were infants.

Hayes called Pollard "a great person overall, a great mother" who "never really did anybody wrong."

He said at one point Pollard had about 10 cats.

"I'm just hoping right now that she's still with us and she's able to come back to us," he said before the Wednesday evening news conference.

Police said they found Pollard's car parked behind Monday's Union Restaurant in Marguerite, about six metres from the sinkhole.

Hunters and restaurant workers in the area said they had not noticed the manhole-size opening in the hours before Pollard disappeared, leading rescuers to speculate that the sinkhole was new.

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

Searchers accessed the mine late Tuesday afternoon and dug a separate entrance out of concern that the ground around the sinkhole opening was not stable.

Pollard lived in a small neighbourhood across the street from where her car and granddaughter were located, he said.

The young girl "nodded off in the car and woke up. Grandma never came back," Limani said. The child stayed in the car until two troopers rescued her. It's not clear what happened to Pepper.

A sinkhole is an area of ground that has no natural external surface drainage and can form when the ground below the land surface can no longer support the land above, according to the U.S. Geological Survey.

The land usually stays intact for a period of time until the underground spaces just get too big. If there is not enough support for the land above the spaces, then a sudden, dramatic collapse of the land surface can happen.

Decades-old mine nearby

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

A team from the Pennsylvania Department of Environmental Protection, which responded to the scene, concluded the underground void is likely the result of work in the Marguerite Mine, last operated by the H.C. Frick Coke Company in 1952. The Pittsburgh coal seam is about six metres below the surface in that area.

Department of Environmental Protection spokesperson Neil Shader said the state's Bureau of Abandoned Mine Reclamation will examine the scene after the search is over to see if the sinkhole was indeed caused by mine subsidence.

In June, a giant sinkhole in southern Illinois swallowed the centre of a soccer field built on top of a limestone mine, taking down a large light pole and leaving a gaping chasm where squads of kids often play. No one was hurt.

In 2023, a sinkhole that in 2013 fatally swallowed a man sleeping in his house in suburban Tampa, Fla., reopened for a third time, but it was behind fencing and caused no harm to people or property.