JOHANNESBURG (AP) — South African customs officials have seized more than $3.5 million worth of rhino horns at the O.R Tambo International Airport in Johannesburg on Thursday. A shipment of the 18 pieces of horns weighing 63 kilograms (139 pounds) destined for Malaysia was discovered at the airport’s courier facilities. The package was labeled “HP cartridges” but an x-ray scan revealed images resembling horns so the customs officials inspected it to discover the contraband, the South African Revenue Services said in a statement. This is the fourth rhino horn bust at the airport by customs officials since July last year, with a total of 277 kilograms (611 pounds) of rhino horn worth more than $15 million confiscated, said the statement.