The Round Rock Police Department is investigating an early morning accident that killed the driver of an 18-wheeler Tuesday morning.

Police said the accident happened near Interstate-35 and Westinghouse Road.

The truck was carrying a load of lumber and the driver was the only person in the vehicle.

The main lanes of I-35 are still open but the southbound access road between Westinghouse and RM 1431 was closed as of early afternoon.

Police have not released the identity of the driver. No other injuries were reported.