UNITY TOWNSHIP, Pa. — The team looking for a missing Pennsylvania woman believed to have fallen into a sinkhole has determined that an abandoned coal mine is too unstable for people to safely search underground, authorities said Wednesday as they expressed hope that Elizabeth Pollard will be found alive.

A large team has been trying to locate Pollard, 64, for two days. Her relatives reported her missing early Tuesday and her vehicle with her unharmed 5-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 40 miles 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."

Trooper Cliff Greenfield said crews were still actively searching for Pollard.

"We are hopeful that she's found alive," Greenfield said.

Searchers are using electronic devices and cameras as surface digging continues with the use of heavy equipment, he 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 30 feet 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."

Pollard's family called police at about 1 a.m. Tuesday 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.

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