RAINIER, Ore. — An 11-year-old boy was seriously injured Monday night after a go-kart he was riding in while being towed behind a pickup truck crashed into a tree and tumbled down an embankment.

The child was transported by helicopter to Emanuel hospital and was still in intensive care Tuesday morning.

The child's uncle, 22-year-old Brandon McKay, was the one driving the truck that was pulling the go-kart, and called authorities after the crash. Police said he voluntarily submitted to alcohol and drug testing and that preliminary results indicated no signs of intoxication.

McKay told police he drove to the intersection of Nicolai Cutoff Road and Wilbur Road at about 8:50 p.m. to tell his nephews it was time to come home. He said the boy asked if he would hook up the go-kart to his truck and pull him.

After tying a long rope to the front of the go-kart and then to the back bumper of his truck, McKay started pulling the go-kart with the boy in it, who said he would steer. McKay said the boy was wearing a go-kart harness and a helmet.

He started towing the go-kart at a speed of between 15 and 20 miles per hour but noticed the cart was veering to the right side of the road. McKay said he stopped the truck, but the cart kept going, hit the tree on the side of the road and tumbled down the embankment, flipping over on its side.

McKay told police he ran to where the boy was and called 911. He said the child is his nephew and is visiting his grandparents in the Rainier area. The boy lives with his parents in Portland.

The cause of the crash is still under investigation.