Who left this emaciated dog at the shelter?

Denver Animal Protection officers are trying to find the couple that dropped off a "severely emaciated" dog at the Dumb Friends League.

The photo of the dog will break your heart.  

The gray-and-white Labrador/pit bull mix weighed just 19 pounds when she was left at the shelter. She should weigh about 35 pounds, based on her height and breed, experts said.

Officials say the dog, now named Petunia, was "near starvation."

"I've been here 20 years and this is the worst case [I've seen]," said Sgt. Stephen Romero, a Denver Animal Protection officer.

Veterinary staff examined the 2-year-old dog and ruled out any health conditions that could have caused her to be so skinny.

Petunia is now in the care of DAP and has put on some muscle mass, but is still very skinny, as you can see in these photos taken Thursday night.

There is no information available about when she may be healthy enough for adoption.

"With a lot of care and TLC she'll be fine," said Romero. 

A man and a woman were seen leaving Petunia in the drop box at the Dumb Friends League on Feb. 17. They are not considered suspects, but animal protection officers would like to speak with them.

"We just want to see if they can tell us where the dog was found," said Romero. 

This is being investigated as an animal cruelty case and Crime Stoppers is offering a reward of up to $2,000 for tips that lead to an arrest.

Convictions in animal cruelty cases could result in fines from $1,000 to $100,000 and/or six months to six years in jail.

If you have information related to this case, please call Crime Stoppers at 720-913-STOP.