A tractor-trailer carrying about 46,000 pounds of pipes buckled at about 1:30 p.m. Tuesday on South Sharpsville Avenue near State Street, Sharon, after the trailer came unhooked. There were no injuries.

The tractor-trailer was headed up a hill toward a pipe yard in Sharon when the king pin gave out, said JT Express driver Matthew Burk of Nashville. King pins are long pins which slide in and lock the trailer and the truck together. State police said the king pin was either not locked or defective, which caused the tractor-trailer to collapse.

Burk said if the king pin had not buckled, he could have cranked the truck back up himself.

"This has never happened before," he said.

Jon Sloan, 30, a nearby Sharon resident, said he was on the computer in his bedroom when he heard a loud crash.

"I heard it through my bedroom window. I thought nothing about it when I heard it until I saw the flashing police lights," he said.

"I came to see if he needed help," he added.

A 14-year-old boy said he saw the truck coming up the hill and watched the middle section "fall off."

"It shook the ground," he said.

State police assisted Sharon police at the scene.