They hold the mysterious contents of all that was left inside China's banks when Mao Zedong's People's Liberation Army marched into Shanghai.

While in 1917, Russia's Communists made the most of propaganda by opening up and revealing what was stored in the country's banks, the Chinese Communists decided otherwise.

'There were 31 banks in old Shanghai which had safe deposit storerooms,' explained one of the guardians.

'In the 1950s, the contents of all them were taken here and kept for safekeeping,' he said.

'I can't tell you how many or what they contained. We have regulations and must respect the confidentiality of our clients.' Officials dismiss stories that during the restoration of some of the old bank buildings on the Bund, workers have uncovered vaults stuffed with diamonds and gold bars left behind by the fleeing Kuomintang leaders.

'There are a lot of rumours going around but it is all nonsense. There are no such treasures left behind by Song Meiling or T.V. Sung,' said Li Weihua, an official with the Shanghai Bund Buildings Function Transformation Corp referring to Kuomintang leader Chiang Kai-shek's widow and to the former party treasurer.

Some of the treasure rumours have been generated by the extensive renovation taking place at the former headquarters of the Hongkong and Shanghai Bank, which were taken over by the Communist Party.

Among the former party secretaries of Shanghai who had their offices in the building were President Jiang Zemin and Premier Zhu Rongji.

The imposing building now serves as the headquarters of the Pudong Development Bank which has refurbished the ground floor to its former glory and installed a new safe deposit store room.

Work is still going on to restore the upper floors of the building .

'The [Communist] Party archives were temporarily kept in the old bank vault but the former deposit boxes were taken away,' said Mr Li.

The Shanghai Bank building now occupied by the Industrial and Commercial Bank of China has remained in continuous use as a bank and staff said the vault was still being used.

'Even in the Cultural Revolution when Red Guards came here, we did not let them in and open the boxes,' said a staff member.

She denied that any of the safe deposits belong to foreigners but said many owners came back immediately after 1979.

'Quite a few came from Hong Kong, later there were others from Taiwan.' Proving ownership has proved a problem for some as the original customers had since died.

'You have to have a key and valid death certificate of the original depositor. Sometimes we have had to turn people away,' said another staff member who worked at the bank for more than 20 years.

Last year some South Koreans were turned away when they could not prove the legitimacy of their claim.

On the other hand, rental charges have been kept low.

'It is cheap. For a small box it is one yuan [about 93.07 HK cents] a year but for the largest box, it is only 20 yuan,' one of the staff members said.