Baltimore police opened an animal abuse investigation last week after someone set a bag on fire while a small dog was inside and left it to die, authorities said on Monday.

The dog, described to WBAL as a small terrier mix, was found around 12:30 a.m. Wednesday after officers were called to a report of a fire in northeast Baltimore.

Officers spoke to firefighters on the scene, who said they put out a burning bag. Inside the bag, firefighters found a dog.

Authorities pronounced the dog dead at the scene and animal control officers were called.

"Investigators believe an unknown suspect, or suspects, placed the dog inside the bag and then set it on fire," police said in a news release. "The suspect or suspects then left the scene."

Authorities did not identify anyone believed to be involved in the case.