Police closed streets and sidewalks around CNN Centre in downtown Atlanta as they investigated a chemical bomb threat, but found no such device during a search of the complex.

Atlanta police spokeswoman K.Y. Jones said no chemical was located in the Friday morning search. She said shortly after 6am that all streets in the area were open again.

Police say a caller claimed to have planted a chemical bomb at the cable news channel's headquarters.

Police had closed streets and sidewalks to vehicles and pedestrians on the block to the north of the center, and on the block to the west of the center.

The complex is home to CNN and several restaurants and shops. The area is just south of Centennial Olympic Park.