AUGUSTA — A 2-year-old boy died Monday when the car in which he was riding hit a building, causing some wooden beams in the back of the vehicle to slide forward and slam into the child’s head and back.

Alex C. Chan was pronounced dead at 3:15 p.m. of a head injury, said Mary Plumer, spokeswoman for Kennebec Valley Medical Center.

Augusta police said the accident occurred shortly after 2 p.m. when a station wagon driven by the boy’s mother, Kitty Chan of Augusta, went out of control near Sewall Street and struck the Rotary Cleaners building.

The impact caused four 6-inch-by-6-inch beams in the back of the car to surge forward, striking the boy in the head and upper back, according to a police report. The child was riding in the front seat, police said.

There appeared to be no child-safety seat in the vehicle and it was not known if the boy was restrained by a seat belt, police said.

Mrs. Chan told police she lost control of the vehicle after the car’s engine stalled and the brakes failed. State police said they would examine the car for mechanical defects this week.