A 9-year-old boy suffered critical injuries Thursday night when he hit his head while diving into a pool in Prince George’s County fire officials said.

The accident happened in the 6100 block of Blue Sage Lane in Upper Marlboro about 7:30 p.m., said Asst. Chief Ron Bridges, a spokesman. The child was taken to a hospital in critical condition.

It was not immediately clear how deep the pool was or if the child was alone at the time of the accident, officials said.