A Pennsylvania grandmother, Elizabeth Pollard, is believed to have fallen into a large sinkhole while searching for her missing cat, Pepper, according to authorities.

The 64-year-old disappeared on the evening of Monday, Dec. 2, in Unity Township, Pennsylvania, after venturing out around 5 p.m. to look for her pet. Concerned for her safety, a relative reported her missing early the next morning, just before 1 a.m. on Tuesday, Dec. 3, Pennsylvania State Police Trooper Steve Limani stated during a press conference, as reported by ABC News.

Authorities discovered Pollard’s 5-year-old granddaughter still inside the parked vehicle when they arrived, according to The New York Times. The car was located near a newly formed giant sinkhole, leading first responders to suspect that Pollard may have fallen in.

The little girl was found safe and told authorities she fell asleep and woke up; but, her Grandma never returned.

“At that point in time, we realized this could be a very bad situation,” Limani told reporters.

“It appears that it was most likely created during the time while, unfortunately, Ms. Pollard was walking around. We’re hoping everyone keeps their family in their prayers, that this ends up being a rescue mission, and that’s how we’re going to continue to conduct ourselves.”

Authorities are deploying heavy machinery and sound-monitoring equipment in the search for a Pennsylvania grandmother who is believed to have fallen into a sinkhole. The sinkhole leads to fragile, unstable ground, complicating rescue efforts.

Rescuers are working to mitigate the risk of further collapse by pumping water through a long-abandoned mine at the site. This process helps clear out debris, which is then removed with a vacuum to improve visibility underground, according to a statement from Pennsylvania State Police early Wednesday.

“The integrity of that mine is starting to become compromised,” Trooper Steve Limani said.

Rescuers remain hopeful that Elizabeth Pollard, 64, may still be alive in an air pocket within the sinkhole. Officials have noted that the hole contains plenty of oxygen and maintains a temperature of about 55 degrees—much warmer than the conditions above ground. Despite the challenge posed by shifting ground, state police have vowed to continue the search until they find answers.

A federal database indicates that two abandoned mines are located near the sinkhole, both classified as posing “the highest danger to citizens’ lives” due to safety and environmental risks, according to the National Association of Abandoned Mine Land Programs.

Sinkholes typically form when groundwater gradually erodes the underground rock that stabilizes the soil. Pennsylvania is particularly vulnerable to sinkhole damage because of its limestone bedrock, according to the U.S. Geological Survey