DETROIT (REUTERS) - A four-year-old Detroit boy died when his cousin, also 4, accidentally shot him while playing with a rifle she found inside a relative's home, police said on Friday.

The children, whose names were not released, were visiting their grandparents' home Thursday afternoon when the four-year-old girl found the gun, Detroit police Officer Nicole Kirkwood said.

The girl was playing with it when she accidentally shot her cousin in the torso, Mr Kirkwood said. The boy was pronounced dead after being taken to a nearby hospital, she said, while the girl was not injured.

The grandparents were not home at the time and had left the children in the care of a family friend, Mr Kirkwood said.

The incident is being investigated, she said.