The leg of a 4-year-old was severed Wednesday when he was struck by a tractor mower, according to Lehigh Township police.

Police and Northampton Regional EMS responded to the 200-block of Walnut Drive around 7 p.m.According to family members, the grass was wet and the child slid under the back of the lawn tractor.The tractor was running and the driver was backing up when the incident occurred.The leg was severed at the thigh, police said.The child was flown by PennStar to Lehigh Valley Hospital-Cedar Crest for treatment.No further information on the child's condition is being released.