Authorities are investigating after a 4-year-old boy was seriously injured after being struck by a boat propeller while swimming in Douglas Lake.

The incident was reported about 3 p.m. Sunday near Dandridge in Jefferson County as the child was swimming with his Sevierville father and two other children, both under the age of 8, according to a Tennessee Wildlife Resources Agency news release.

A rented pontoon boat the group was swimming from began to drift away in the wind.

A 28-year-old Knoxville woman onboard the boat started the engine and began moving back toward the swimmers. The boy, whose name has not been released, was struck in his upper left arm and shoulder by the propeller, the release states.

The child was flown by Lifestar helicopter to the University of Tennessee Medical Center. His condition was not immediately available Monday morning.

No other injuries were reported.

TWRA is investigating.