Reaching a dramatic culmination on Monday, more than 300 officers were involved in simultaneous swoops at seven addresses in some of London's most illustrious neighbourhoods. And, as they emerged from the raids clutching thousands of innocuous-looking safety deposit boxes, the detectives leading Operation Rize couldn't help but wonder what was inside.

Yesterday, as the Metropolitan Police Specialist Crime Directive revealed the storage facilities' contents, their questions were answered. The raids had yielded a haul so remarkable, even Scotland Yard's most seasoned were stunned.

A spectacular collection of jewellery, Renaissance paintings and millions of pounds in cash were seized from the locations in Park Lane, Hampstead and Edgware. The ill-gotten gains – believed to be the proceeds of major organised crime – had been kept hidden in 7,000 deposit boxes for some of the country's wealthiest individuals.

Having searched fewer than half of the boxes in the first three days, officers said that the final total was expected to be "astronomical".

Among the goods said to have been secreted away was £16m shoved into plastic bags. Several works of art, sheets of counterfeit £5 notes, passports of different nationalities displaying the same photograph, chequebooks, credit cards, diamonds and a gun were also found.

Yesterday, armed police remained outside the safe depositories in the capital as officers continued to remove a treasure trove of valuables. It will take days to remove every box and prise it open, using specialist equipment, before its contents can be taken to a secret, secure, storage facility. Working day and night, officers have been logging each item, examining the goods found within every container – which range in size from shoe-box holders to walk-in vaults – to recover forensic evidence. Meanwhile, experts were yesterday trying to establish the authenticity of the works of art and whether some of the jewels may be legitimately owned.

While Operation Rize is a money-laundering investigation, detectives believe some of the items found in the deposit boxes could offer clues to a variety of crimes from murders to drug trafficking, paedophile gangs to serious fraud. Many of the passports are women's, leading officers to believe they may have been used in a prostitution ring.

Commander Allan Gibson said: "Operation Rize is a huge under-taking and we are still in an early phase of the inquiry. Search teams have been working around the clock to open all the boxes at the location and are progressing well, although we are likely to remain at the locations for some time yet.

"This is a complex and unique investigation that will use all of the expertise within the economic crime command and the findings are within our expectations at this stage. I am confident this operation will have a damaging impact on organised crime in London and around the rest of the country."

Most of the boxes are believed to have been used by a range of criminals, though officers conceded some innocent members of the public had been caught up in the case. They had, they explained, been inundated with phone calls from box owners as they try to sort legitimate property from the spoils of criminal activity.

Two directors of the company Safe Deposit Centres Ltd, Jacqueline Swan, 44, and Leslie Sieff, 60, were arrested on suspicion of money-laundering offences and bailed to return to a central London police station in early September.

Two other men arrested for obstruction have since been released without charge.

Safe Deposit Centres Ltd was established in 1986 by four businessmen in north London. One of the men, Milton Woolf, 52, is still a director. The firm's web site boasts: "Unlike banks, our service is completely designed for private safekeeping. We know you may often need access at short notice, so we're open long after business and banking hours, 7 days a week, 363 days a year. Box access is free and unlimited and once your identity has been verified, using manual and electronic means, you may proceed immediately with no queues, waiting or fuss.

"Our centres provide a wide and varied range of safe deposit box sizes. Whether it's jewellery, cash, documents or computer data... there will always be one to suit your needs exactly."

The Met Assistant Commissioner John Yates, who led the investigation into the "cash for peerages" affair, has said the centres could be linked to criminal activities from paedophilia to drug trafficking.

"Operation Rize is a huge undertaking by the Met to tackle criminal networks who we believe are using safe deposit facilities to hide criminal assets. In the main, this industry operates legitimately, and it is in the public interest that we target this particular business to stop any criminal activity."

Those wishing to collect their items should contact the police call centre on 0800 030 4613

www.belfasttelegraph.co.uk/news/local-national/article3766836.ece