An 8-year-old boy accused of stabbing his great-grandmother three times in the back Sunday night was being held for a mental-health evaluation, Cheltenham Township police said Monday.

Police said that the boy, who was not identified and may be suffering from a mental illness, attacked his older relative with a knife before 9:30 p.m. Sunday. The attack was not provoked, and no argument preceded it, police said.

Lt. John Frye, head of the Cheltenham Police Detective Division, said in a prepared statement that officers were called to meet Philadelphia police at Jeanes Hospital about a woman who had been stabbed in the back.

Frye said investigators determined the stabbing took place in a residence in the 7400 block of Fourth Avenue in Cheltenham, where the boy lives with his mother and great-grandmother.

The victim, who is 54, required two staples to close one stab wound; the other wounds were superficial, Frye said.

"The attack was unprovoked, and the male is being treated for some type of mental illness," Frye wrote in an e-mail. "It's very early in the investigation, so that is all we have right now."

The boy was referred to a facility in Montgomery County for a mental-health evaluation, Frye said. Juvenile unit officers and detectives are investigating.