State police investigate an apartment complex where five members of a family, including three children, were found dead in Saco, Maine. Picture: Robert F. Bukaty

Saco, Maine -

A family of five, including three children from 4 to 12 years old, were found shot to death on Sunday inside a US apartment, authorities said.

Investigators said a gun was found near one of the bodies, and it appeared no one outside the family was responsible for the shootings.

Maine State Police Sergeant Chris Harriman said murder-suicide is one of the scenarios being investigated, but that determination will be made by the state medical examiner's office.

Investigators said a family friend had contacted a worker at the apartment complex worried about the well-being of the family. The worker entered the apartment and discovered one body, then immediately called police.

Police found the bodies in three different rooms. Police described the firearm found in the apartment as a long gun. Shell casings were also recovered.

Officials said autopsies were scheduled for Monday. - Sapa-AP