A 2-year-old girl was pronounced dead after being found outside a New Hampshire apartment building Monday morning in below-freezing temperatures.

Newport police are investigating whether the girl might have left the Maple Street apartment through a back door overnight and then couldn't get back in.

A neighbor told the Valley News that he heard crying around 4 a.m. but didn't see anything. He said he and his girlfriend later found the child just after 7 a.m. Police said the girl was found wearing her pajamas near the building's back steps.

Temperatures overnight in Newport were below zero.

The girl's grandfather, Lindsay Van Schoick, identified her as Sofia Van Schoick. He told NBC10 Boston that his daughter and two grandchildren had just moved in with him over the weekend.

Van Schoick said Sofia wasn't familiar with the house and that might be why she wandered down the stairs and ended up getting trapped outside.

Sofia had a twin brother, who was inside the home at the time.

Police said the death appears to be "a bad accident."

Newport Police Chief Jim Burroughs said it's unclear whether anyone will face charges in connection with the girl's death. Preliminary autopsy results show that the girl likely died from exposure to the elements.

"It was 8 below zero overnight here in Newport at the scene," said Burroughs. "The investigation is very much ongoing at this time and cause of death has not been determined. Right now everything appears to be consistent with exposure."

Burroughs said this is one of the most tragic cases he's ever investigated in his decades in law enforcement. He said the death has had an impact on the first responders.

"A very unfortunate set of circumstances that involves a 2-1/2-year-old young girl who left the residence apparently by her own accord and just wasn't able to regain entry," Burroughs said.

The investigation is ongoing.