Four suspects accused of robbing travellers after following them from OR Tambo International Airport were arrested over the weekend during a joint intelligence-driven operation, police said. Members of the police's national investigation unit, with the assistance of Parkview detectives, were following up on information about a suspect involved in an armed robbery case at the airport last week when they made a breakthrough."This led to the arrest of four suspects aged between 25 and 45 at various residences in the area of Hillbrow," said police spokesperson Colonel Katlego Mogale in a statement."The team also recovered a .38 special revolver, five rounds of ammunition as well as suspected stolen property including a passport, suitcases, clothing and a Lenovo notebook."ALSO READ: Woman caught with drugs stashed in cereal boxes at OR Tambo International AirportMogale added that police were not ruling out the possibility of the suspects being involved in reported cases of robberies taking place after victims were followed from the airport."Further investigations are being conducted in this regard. This should serve as a reminder to criminals that it is only a matter of time before they are identified and arrested."The four suspects are expected to appear in the Johannesburg Magistrate's Court on Monday on charges of armed robbery and theft.Rhino horn bustLast Thursday, police also seized a large haul of rhino horn worth over R23m at OR Tambo International Airport."The total weight of the horns was 116kg ... at an approximate value of R23 200 000. The street value of these horns is assumed to be much higher," the South African Revenue Service's Sicelo Mkosi said in a statement on Thursday.READ: Rhino horn worth millions seized at OR Tambo before take off to DubaiThe discovery was made during K9 searches at several cargo warehouses where export consignments were packed to be shipped out to Dubai.Mogale said a K9 detector dog had reacted positively to a shipment destined for the Middle East.Three drug mules were also nabbed at the airport earlier this month.News24 previously reported that the three travellers were all caught before departing for international destinations.One of the alleged smugglers has been accused of swallowing several synthetic "bullets" containing cocaine while the other two had drugs hidden in their luggage.