PITTSBURGH — Officials in Pennsylvania are searching underground for a woman who is believed to have fallen into a 30-ft (9m) deep sinkhole that may have opened up below her feet as she was searching for her lost cat.

Elizabeth Pollard, 64, was reported missing by family members after she went out to search for the cat on Monday night.

Officials who arrived first to the scene nearly fell into the same hole, which they say is connected to an abandoned coal mine.

Microphones and cameras have been lowered into the hole, but Pollard has yet to be found. Officials say their cameras spotted what appeared to be a shoe.

Pollard's car was found parked behind a restaurant in the town of Marguerite, 40 miles (65km) east of Pittsburgh, early Tuesday morning.

Her five-year-old granddaughter was inside the car, officials said, adding that the girl was cold but not hurt.

Pennsylvania State Police Trooper Stephen Limani told reporters that the hole is about the size of a city manhole cover.

"It was about the size of manhole cover but the pocket underneath is significantly larger, and trying to send cameras down there, we determined it's roughly about 30ft before you see a lot of debris," Limani said.

Officials believe that the sinkhole opened up as Pollard was standing on top of it while looking for her cat named Pepper. They hope that she is sheltering in an underground "void".

"The sinkhole, it appears that it was most likely created during the time, unfortunately, that Mrs Pollard was walking around," Limani said.

"We don't see any evidence of any time where that hole would have been there prior to deciding to walk around and look for her cat."

More than 100 people were assisting in the rescue on Wednesday, he added. Mining experts from the state government are also on the scene, and officials have dug an additional hole in order to be able to access the site, which they fear is unstable.

Temperatures, which have been below freezing the last several days, are much warmer inside the hole than they are at the surface. Authorities have also not detected any dangerous gases that are sometimes found in abandoned mines.

Pleasant Valley Volunteer Fire Company Chief John Bacha told reporters that the shoe likely found does not appear to date back to when the mine was still operational.

“It’s a modern shoe — not something you’d find in a coal mine in Marguerite in 1940,” he said, according to NBC News. — BBC