A crane operated by Polk Crane Service, of Lawrence, is tipped backward at a home construction site in Baldwin. No one was in the truck cab when something caused the boom to go down and strike the wall of a storm shelter being built in the house, said Greg Polk, co-owner of the company. There were no injuries in the accident. Other trucks and a crane were called to the scene and used to bring the truck back to the ground, Polk said. The crane was dismantled and the cause of the accident is being investigated by Altec, a crane manufacturing firm in the Kansas City area. The crane has a "black box" that records data about the crane's operation similar to boxes found on airliners, Polk said.