Authorities at Kotoka International Airport have tightened security following the interception of 38.5 kilograms of narcotic substance suspected to be cocaine, the second such seizure in a week.The substance was discovered on Wednesday.Joy News sources at the airport said the substance was hidden behind one of the refrigerators at the duty-free shop of the airport.Another 40 kilograms of cocaine was discovered at the same duty-free shop exactly one week ago.Airport authorities have therefore announced increased vigilance on the staff following the discovery but no one has been arrested in connection with the latest cocaine discovery.But Joy News sources say airport officials believe the three airport staff arrested last week for the attempted smuggle of 40 kilos of the drug might be behind this latest discovery.The Acting Deputy Director General in charge of Finance and Administration at Civil Aviation, William Orhin who confirmed the latest discovery to Joy News would not say whether any new arrests have been made or the quantity involved.He however would not rule out the possibility that the discovery could be linked to last week's.