'We have already contacted the Japanese customs and expressed our concern,' he said, stressing that Hong Kong customs officers would only use special training luggage for similar exercises.

The blunder occurred at about 3.30pm on Sunday when the officer stuffed 142 grams of cannabis, valued at 1 million yen (HK$75,500), into the side pocket of a randomly selected suitcase arriving on Cathay Pacific flight CX520 with 282 passengers from Hong Kong. But his dog, which was being trained, failed to detect the drug and the officer failed to retrieve the cannabis before the traveller left the airport with his luggage.

Japanese customs authorities apologised, saying: 'Customs feels great regret and we offer our deepest apology. We will also thoroughly investigate the case and punish concerned officers to ensure a repeat of such an incident will not occur.'

Customs said the package was recovered on Monday shortly after 9pm from a Hong Kong traveller in a Tokyo hotel, but did not disclose how the traveller had been found. Officers apologised to the traveller.

Cathay Pacific said it did its best to help officers recover the cannabis. 'We were notified at 8.15pm on Sunday night. And as far as we know, officers tried to contact the passengers by going through passenger information on the customs declaration forms,' an airline spokeswoman said.

'We had not been informed of the training exercise and we believe that the officers should have told us beforehand so that we could co-operate with them.'

Travel Industry Council executive director Joseph Tung Yiu-chung said the council had written to the Japan National Tourist Organisation to express its discontent.

'We have never heard of any similar case anywhere,' Mr Tung said. 'It is a big mistake. What would have happened if the traveller had gone though other customs?'