Johannesburg - A security officer at Johannesburg's OR Tambo International airport was in police custody Thursday after being arrested in connection with the discovery of large quantities of drugs on a South African Airways (SAA) flight to London.

Police said a female security officer was arrested Wednesday night, a day after investigators at Heathrow airport found 50 kilograms of cannabis and four kilograms of cocaine in three pieces of luggage after the arrival of the morning SAA flight.

A senior police official said the suspect faced charges of drug trafficking and violating the Customs Act for allegedly letting drugs leave the country without alerting police.

"Basically she confessed," the police superintendent was quoted by SAPA news agency as saying.

Meanwhile, the 15-member crew of the flight, who were released on bail Wednesday after questioning by British investigators, returned to South Africa Thursday.

The crew have not been suspended but had been taken off flying duties, SAA said Wednesday.

They have been ordered to report to British authorities again on March 23, pending further investigations.

SAA, which is owned by the South African government, has said it has also launched an internal investigation into the affair.

The haul has raised questions about security standards at Johannesburg airport, a major hub for air traffic in southern Africa, that is undergoing a major upgrade in advance of the 2010 football World Cup.

A spokesman for the Airports Company of South Africa told the private eTV news channel Wednesday that security checks of flight personnel was left to their airlines. (dpa)